Terrible service from Cell c & 10k in debt

I had taken up a contract with Cell c for an LG G6 in May 2017, due to being retrenched for 2 months I had failed to make 3 payments and was handed over to "NuDebt" I had made arrangments with them to make a payment of R2400 which was done using their online payment system to set a debit from my account and money reflected and was confirmed by Nudebt I have email proof but then I received a statement from Cell c to say instead of R790 I was now owing 4k. So I reversed the debit order thinking that maybe I have ****med bu then Cellc decided I was in breach of my contract for failing to make payment and cancelled my contract which left me with a huge bill of R10k for cancellation of the contract for being in breach. I have proof on my email to confirm i made the payment of R2400 but reversed it because Cell c said they have not recieved it but Nudebt confirmed they had recieved it. Now i have made apayment arrangement from around August last year to pay R200 a month as that is all i can afford so i decide to sell the phone to recover some of this money to settle some of the ballance only to find out my phone has been blocked or blackjlisted and cant put any sim in the phone to make or recieve calls so now i cant sell the pohone. The value of the phone has even dropped so much that i canonly get about 10% of the amount owing by selling the phone.

How is this fair as aloyal customer who was retrenched at the time, i had made arrang,ment to make payment but i want the phone unlicked and my debt reduced as this was not my fault for the amount not reflecting.

Please unblock this phone and sort my debt out, take the phone back if you have too.

Best Regards Rowan