Bridging of letter

I had a fiber contract with them last year, I gave them notice, a lady called to say that the last payment didn't go through we paid it and ask them to release the line so we can move to a new SP they say we have to wait two weeks before they release the line to make sure that the account paid in full that is their policy. 6 month later on the 2nd of June we received a email with saying I owed R1028.01 that must be paid with in 21 days from the date of the email. 6 days later on the 10th of June they hand it over to legal department and by the 18th of June I had to pay R1128.08 i did pay to avoid accumulation. I try to call Cell C to solve this issue but as usual has been put from department to department wasting my airtime.