account paid, but vodacom still says I havent.

My contract was ****** in November 2012. It was suspended due to my account being in the arrears. On the 31/07/2013 I emailed Vodacom to say that I wanted to settle the account on the 31/07/2013 or the 01/08/2013. Being so long ago, I don't know if it was paid on those exact dates, but the day I went to pay a loan I paid Vodacom as well at a standard bank. I cant confirm the amount as I have moved and lost the slip. But after I paid, I considered the account to be paid in full and dealt with. In may 2014, I tried to get a loan from my bank to relocate, but I showed that I had an outstanding amount with Vodacom of R2500. I emailed them and again on the 26/06/2014 demanding what amount I still owed and where it came from. By that time I had relocated to Bloemfontein. Nothing more becomes of this. I get contacted in april 2015, stating that I owe R4500 to Vodacom for an outstanding accounts. I asked the lady why I owe and why I am I getting contacted a year and a half after the payment that I still owe. She said the account get handed to collectors and some don't call. I don't have proof of payment, but I am trying to get standard bank to get their copy. Maybe Vodacom needs 2 recheck.