Limit was increased without my approval

At the end of JAN 2016 I was debited with 309. for for Dec & Jan. my contract is R99 a month With no spend limit.I called to query & they said in Dec sms were sent to say that the limit will be increased if no response is received. Actual cell is being used by my nanny who was at home at that time. So she did not reply no -the sms did not state reply no. I got my bill on the 3 feb & they debited my account with 309 & I owe them 294 by the end of feb. I called & they said they will send a request to have the amount refunded. The refund was for amount 309 and 195.The ref no was ***9. Turnaround time 7 days. I requested an email and not a call. No response recieved. I called again yesterday 24 feb for a response for refund request. .My request said the full refund of 375 & only refunded R180. my contract is 99 per month & 3 months have passed that is 290. I paid them 309 at the end of jan why do I owe them 114 at the end of feb. spoke to a manager Francina for an 1hr solution was to send another refund request. new REF no ***3. How can Telkom keep increasing my limit