TERRIBLE SERVICE

I have a JET account which, I requested the balance of the account to be forwarded to me via sms which I received. I went the same day to pay the outstanding amount to close my account. A day later I received my account statement with a different amount on. I contacted Nimble and explained that I have paid the requested amount. They cliamed not to have received my payment and asked that I email it to them (which I did). A few day later I received a call from one of the agents asking me to pay my account as it is in arrears. I explained again that I paid my account and was again asked to forward proof of payment, which I sent again. I have since emailed and whatsapped my proof of payment probably over times. Still no acknowledgement of payment received and the amount still reflects on my account. I have called many times just to be told it is being exculated..... I dont know what more to do