Unable to exit Sql cursor - sql

Question

This is hard for me to explain but I have tried my best to make it as easy for you all as I can.
I have two tables. One stores information about customer tbl_installations. Another his internet bills tbl_bills (this one is more important).
tbl_installations
CREATE TABLE [dbo].[tbl_installations](
[SrNo] [int] IDENTITY(1000,1) NOT NULL,
[name] [varchar](200) NULL,
[email] [varchar](100) NULL,
[phone] [varchar](20) NULL,
[plandesc] [varchar](50) NULL,
[plancost] [money] NULL,
[amtpaid] [money] NULL,
[amtbalance] [money] NULL,
[address] [varchar](500) NULL,
[referencename] [varchar](20) NULL,
[installationdate] [date] NULL,
[planduration] [int] NULL,
[MkrId] [varchar](20) NULL,
[MkrDt] [datetime] NULL,
[FromDate] [datetime] NULL,
[ToDate] [datetime] NULL,
[ExpiryDate] [datetime] NULL,
[Status] [varchar](20) NULL,
[CustomerId] [varchar](20) NULL,
[ServiceTax] [money] NULL,
[TotalAmt] [money] NULL
) ON [PRIMARY]
tbl_bills
CREATE TABLE [dbo].[tbl_Bills](
[Srno] [int] IDENTITY(1,1) NOT NULL,
[CustomerId] [varchar](20) NULL,
[PlanDuration] [int] NULL,
[Amount] [money] NULL,
[PaidAmt] [money] NULL,
[discount] [money] NULL,
[PlanDesc] [varchar](20) NULL,
[FromDate] [datetime] NULL,
[ToDate] [datetime] NULL,
[MkrId] [varchar](20) NULL,
[MkrDt] [datetime] NULL,
[ServiceTax] [money] NULL,
[TotalAmt] [money] NULL,
[PendingAmt] AS ([TotalAmt]-([PaidAmt]+[discount])),
[PaidStatus] [varchar](10) NULL
) ON [PRIMARY]
THIS SCRIPT WILL GIVE YOU DATA THAT I HAVE:
insert into tbl_installations(name,email,phone,plandesc,plancost,amtpaid,amtbalance,address,referencename,installationdate,planduration,MkrId,
MkrDt,FromDate,ToDate,ExpiryDate,Status,CustomerId,ServiceTax,TotalAmt)
values('Gulzar','asdasd','3242342',null,null,null,null,'asda asd aada','ref name',GETDATE()-4,1,'arbaaz', GETDATE(),null,null,
null,'INSTALLED','C2002',null,null )
insert into tbl_bills (PlanDuration,Amount,PaidAmt,discount,PlanDesc,FromDate,ToDate,PaidStatus,MkrId,MkrDt,ServiceTax,TotalAmt,CustomerId)
values(1,800,600,0,'1MB',GETDATE()-4,DATEADD(month,1, GETDATE()-4),'PAID','Arbaaz',getdate(),800*(12.36/100),800+800*(12.36/100),'C2001')
PendingAmt in tbl_bills is a computer column which calculates the pending amount based on totalamt - (paidamt+discount)
tbl_bills.Amount is the subsription cost eg: 800
tbl_bills.TotalAmt is sum of Amount+ServiceTax
Scenario
First Month:
Customer's subsription cost(Amount) is 800
PaidAmt=600
ServiceTax=98.88
TotalAmt=898.88
PendingAmt=298.88(computed field)
Second Month:
Customer still has same subscription worth 800 (total 898.88)
But he pays 1100 so that he settles some of pending amount.
This 1100 must first settle all the previous pending amounts first(by updating tbl_bills.paidamt and then what ever is left should be inserted as a brand new row in the same table.
HERE IS MY FAILED ATTEMPT :
THIS KEEPS ON RUNNING ENDLESSLY
declare #srno as int=0
declare #Cid as varchar(20)='C2001'
declare #PlanDuration as int=1
declare #Amount as money=800
declare #PlanDesc as varchar(20)='1MB'
declare #FromDate as datetime ='2014-11-11'
declare #ToDate as datetime='2014-12-11'
declare #PaidStatus as varchar(20)
declare #MkrId as varchar(20)='arbaaz'
declare #status as varchar(20)='PAID'
declare #Discount as money=0
declare #PaidAmt as money=1100
--as
if(#status='INSTALLED')
BEGIN
insert into tbl_bills (PlanDuration,Amount,PaidAmt,discount,PlanDesc,FromDate,ToDate,PaidStatus,MkrId,MkrDt,ServiceTax,TotalAmt,CustomerId)
values(#PlanDuration,#Amount,#paidamt,#discount,#plandesc,#FromDate,#ToDate,'PAID','Arbaaz',getdate(),#Amount*(12.36/100),#Amount+#Amount*(12.36/100),#Cid)
if((select sum(PendingAmt) from tbl_Bills where CustomerId=#cid)=0 )
begin
update tbl_installations set Status='PAID' ,ExpiryDate=#ToDate where CustomerId=#Cid
end
else
begin
update tbl_installations set Status='UNPAID' ,ExpiryDate=#ToDate where CustomerId=#Cid
end
END
ELSE
BEGIN
declare #pAmt as money
select #pAmt=sum(PendingAmt) from tbl_Bills where CustomerId=#Cid
declare #Amt as money =#Amount
select #Amt=#Amt
--select srno from tbl_Bills where CustomerId=#Cid and PendingAmt<>0 order by ToDate
if(#pAmt>0)
BEGIN------------------------
DECLARE #ColExpir datetime
DECLARE #ColFallprotec datetime
DECLARE #CurSrno int
--------------------------------------------------------
DECLARE #MyCursor CURSOR
SET #MyCursor = CURSOR FAST_FORWARD
FOR
select srno from tbl_Bills where CustomerId=#Cid and PendingAmt<>0 order by todate
OPEN #MyCursor
FETCH NEXT FROM #MyCursor
INTO #CurSrno
WHILE ##FETCH_STATUS = 0
BEGIN
IF(#Amt>0)
BEGIN
declare #PendingAtCurSrno money
select #PendingAtCurSrno=pendingamt from tbl_Bills where SrNo=#CurSrno
print #CurSrno -----
print #PendingAtCurSrno ----
if(#Amt>#PendingAtCurSrno)
begin
update tbl_Bills set PaidAmt=TotalAmt where SrNo=#CurSrno
select #Amt=#Amt-#PendingAtCurSrno
print '1st'----
print #amt----
if(#amt=0)
begin
CLOSE #MyCursor --tried break and return here too
DEALLOCATE #MyCursor --
end
end
else
begin
update tbl_Bills set PaidAmt=paidamt+#Amt where SrNo=#CurSrno
select #Amt=0
print '2nd'
print #amt----
if(#amt=0)
begin
CLOSE #MyCursor --tried break and return here too
DEALLOCATE #MyCursor
end
end
END
END
FETCH NEXT FROM #MyCursor
INTO #PendingAtCurSrno
END
CLOSE #MyCursor
DEALLOCATE #MyCursor
END-------------------------
if(#Amt>0)
begin
insert into tbl_bills (PlanDuration,Amount,PaidAmt,discount,PlanDesc,FromDate,ToDate,PaidStatus,MkrId,MkrDt,ServiceTax,TotalAmt,CustomerId)
values(#PlanDuration,#Amount,#Amt,#discount,#plandesc,#FromDate,#ToDate,'PAID','Arbaaz',getdate(),#Amount*(12.36/100),#Amount+#Amount*(12.36/100),#Cid)
end
if((select sum(PendingAmt) from tbl_Bills where CustomerId=#cid)=0 )
begin
update tbl_installations set Status='PAID' ,ExpiryDate=#ToDate where CustomerId=#Cid
end
else
begin
update tbl_installations set Status='UNPAID' ,ExpiryDate=#ToDate where CustomerId=#Cid
end
Not only does it keep running endlessly , it keeps updating the paidamt over and over again and never gets to the point where it should insert another row with remaining amount.