Bad service at mtn

Iam struggling to cancel my comtract with mtn, i phned them on the 14of nomemner to cancel my contract which end on the 15th of december, iwas adviced by their consultant to phne them again before the 15th December, to my suprise when iphne them today they tel me that iam now on a month to month i must pay them a cancelation fee of 375 because it will take them 30 days t cancel my contract 🤔🤔🤔🤔, how come, mtn you such a ***** my agreement with you was 36 months and ihave honored it without any hustle, now when iam to be free you wanna give me a run around,. Cancel your contract and iam not paying you any 375 cause i have informed you in time.