Angry and Upset client

I have an MTN top up contract which is not even 2 years old as yet and MTN decides to bill me extra this month and add to my top up airtime which i did not ask for, i tried calling the call centre to enquire about this and no one has answered my calls ( called about 10 times, call also gets cut after few minutes and held on for 1 hour at 1 stage without anyone answering, ) which is very frustrating, then i tried calling the overport city branch where i took out my contract and that number just rings with no answer as well, I went on to the website to check the number I have is correct and I was given an option to send an email which I did and still have not received a response, MTN service is gone from BAD to WORST...i am now thinking of cancelling my contact all together, why be with a service provide that you can never get a hold of when you need assistance.