Single sided renewal on suspended contract ???

I had good contracts with MTN since 2011 until January 2015. I was due to receive my monthly data as usual on the 20th of Jan 2015 and did not receive it. After the 1st I then called their customer line to enquire. They said I had used too much in Dec 2014. They said I had to wait until they debit again on the 28th of Feb 2015, which does not make sense since the contract says they are supposed to give me service every month, and I had never missed payment. I called numerous times during Feb complaining because I had to go a whole month without DATA as I could not top up either. After the 28th they gave me the DATA as usual without including the DATA that they had not given me the previous month. At the end of March they tried debiting my account on the 28th of March even though our contract clearly states that they should debit on the last day of the month as this is when I receive my salary. They then stopped service, never communicated. I called last week and they said my account was with legal even though no letter or bill was ever sent to me. The contracts were expiring May 2015. Now they want me to pay until Sep 2015!! They never serviced since March 2015!!