cell phone contract cancellation

i called mtn to cancel my contract on the 10/07/2015 , my 24 months was up so it wasnt an early cancellation. instead of my d/o reducing it went up to R 400 from R370 , i have been calling mtn ever since for thing querie , im still beinf debitted R400 even this month . these are some of the ref numbers i got *** , *** , ***2 , i was promised a refund , an email , a phone i have heard ZERO from them .