Unable to Cancel Stc Landline Connection Permanently, only the bill will be cont

The year 2010 I used STC landline phone connection, then I’d been cancel the land phone connection with last bill payment in STC landline Office (Thakhsusi branch) the year 2011 December. The STC staff said your landline connection disconnected. After this the year 2013 April I went final exit. Then I return back to KSA with new visa. But the STC People did not disconnect the landline connection and it has to be continue till today and they are sending SMS and giving me bills unnecessarily. What I suppose to do for this issue? Anybody help me Please...