CELL C :UNTRACEABLE DEBT PAYMENT

I have been taking 24 months contracts with Cell C as from 2014 for number *** .. I am now due for a renewal but to my surprise they have declined it due to a debt of 2015 they claim. I was surprised as I took out a contract on 2017 and no outstanding debt was mentioned . I had two contracts in 2015 of which their policy was if you don't pay for the other number they suspend both lines so I had no choice but to pay for both all the time . They said I owe R2000 for that number , They gave me a ref and banking details to pay this debt, fine I paid the R2000 as I need to renew. I then sent them proof of payment with the details. and now they are saying they cant trace the money and my bank says the money is in Cell c account . I am so stressed , there is no renewal and a I have lost R2000 .