Billing errors

We signed up for a Telkom contract Jan 2015 for a 4mg uncapped line. We were paying in the region of R890 incl vat per month. We then had endless issues with not being able to connect. After complaining we were told we were not on a 4mg line even though that's what we were paying for. They then switched us to 10mg line and said it would cost R40 more per month. This was not the case. Bill went up to over R1000. We still had issues with Internet dropping. It then came out our area did not support a 10 mg line so we went back to 4 mg. we also queried the amount we were paying and we were told it was wrong. They then credited my account last month. I have just received the march bill and it is now over R1200. Why does it keep going up when we are told we had been paying too much and we were credited. I am sick and tired of going into Telkom. I don't see how something that was R890 to start can now be over R1200 per month