billing overcharge

our first datakaart which should have been CANCELLED monthly charges of R99 from 2014 jumps 4/2015 to R4139.48 TO R4566.08 5/2015 TO R27856.25 6/2015. The sim by mtn branch shows that it was suspended the 31/5/2015. our main datacard we use suposed 4G and we added a extra 2G 4/2014 jumps from R169.66 5/2012 to R131.51 6/2015 to R6537.71 the 7/2015 but my mtn datacard modem statistics shows we only used 2.74GB received and 941.29MB sent, I struggle to get on the internet and 99% of usage is for banking app and email, we have wi fi but rarely uses it, we logged a quiery at mtn store but NO reply, we have stopped our debit order and will only activate it if these matters have been sorted out, we have been with mtn over 10 years and installed signal boosters after moving on each farm to stay with mtn and even with our poor signal and struggle to actually get onto the internet which may be off for days, we never complaint. But these accounts are unacceptable with no response from mtn, our celphone data has also gone up a lot, but that I can still understand because we use our phones how correct that billing are I can only wonder now