MTN contracts

I had a data contract, Sim card only, for my rooter through MTN. I was paying R199 per month and apparently my contract ended the 17th of September. I received and invoice from MTN on the 18th November via email informing me that my monthly premium had increased from R199 to R320 per month because my contract had ended. I sent an email to customer services asking why no representative had contacted me and advised me my contract had ended or request me to upgrade. The MTN Sim data runs my ADT alarm system and cameras which is for my safety. I am retired and I also have limited funds which I advised MTN customer services via email but to date no one has contacted me telephonically. I never experienced this with my Telkom service provider. My mobile contract ended and they even reduced my monthly fees substantially for my data and calls.