MTN assigning bbundles to my account without my permission

MTN has overcharged me for about 6 months with a recurring data bundle. a time where i was not even the country and also never using my sim card. Ive requested the eveidence or recoding or something indicating to me where i signed up for this bundle. Why should i if i already have a data contract??? I have been to MTN shops about 5 times, tried to phone their contact centre 10 times. sometimes the system is "Offline" or their call quality is so bad i can hardly hear. Sent meassages on twitter, email etc they respond but as soon as i lay my case i hear nothing back?????