unfair billing system

i opened a contract with Telkom. a Router Wifi for R99 a month with benefits of 5gig. the contract resumed on march 16th 2016.on the 15th of april my bank account was debited R210. according to the consultant i spoke to she said i was billed for the whole of month of march and april and was also charged call line identification or itemised billing of about R10.00. hence R210.00. the benefit i received was about 500MB for the month of march. so this means my benefit was prorated for the month of march but my premium of R99 was not prorated. this is not fair because i was not even told that there will be an extra fee to be paid. i would like hello peter to assist me to get back the extra money i was charged.