Collection department complaint

I have a contract with Cell C and it’s the first time I’m having bad experiences with them. I paid my account on the 20th of February because normally I pay upfront or I leave at the debit order go off. and then called on the 3rd of March to find out about my account just to find that my account is in arrears and I told the lady that was speaking to me about my account and it has been paid on the 20th of February and then she said no it shows that it’s not. she gave me email addresses to send my proof of payment to and I have done that but once I sent the emails it came back saying that the email does not exist I again made a phone call speaking to some consultant again that gave me again another email address and again sent everything,After that I started phoning up and down for a week from the 3rd of March until the end of the week just to find out what is going on with my account I send them the proof of payment I did everything that they asked.I told him that they are missing up my credit score and they put my bank account on such a big minus after I told him that I did pay but I kept on deducting. I then got a phone call on the 15th of March at 10:52 from a lady stating that I am in a rears with 109 and I told them if you guys did your job you would’ve known that I did everything that you guys asked and you need to fix my stuff because my credit score is missed and my Bank is in arrears she didn’t drop the call in my ear. I can send them my email on the 15th saying that they should fix their mess and get my things right because I’ve never been in a arrears with Cell C