MTN???????

I am so disappointed with the service I received from MTN, both the customer care line and at the branch. On the 1st of March I received a statement whereby I was billed an insane amount of money on my contract, I called the customer care line only to be told that their systems are not working, visited the branch with the query to request that they suspend and block the sim card as I do not know who is using it, only to be told that it is done but surprisingly April I get high bill and mind you I'm not the one using the sim card, went back to MTN springs mall branch again but still the number was not blocked and I wrote an email whereby I was referred to ***** department who was investigating the matter only to be asked for affidavit and other documents, I submitted the requested documents to be told after 21 days of waiting that it is not a ***** case I should pay the account, can a person use their hard earned money to pay for services he/she did not use. The account is on arrears all because you don't want to clear the issue or investigate further or the matter should be escalated to the ombudsman, I don't know what to do anymore, till this date. Now that I'm not paying the account I'm billed my normal R379 but March was R2287-70, April R3555-51, May also 3000+ and June. Till this day the issue is not resolved. The bad service I received from MTN is out of this world.