my responsibility???

I went to cell c in June to say my phone was ****** and got ITC ref ***5.<br> in the store I had my samsung galaxy to which I needed a sim card and sim swap to continue using my contract till I was eligible for upgrade and when the guy did my checks he confirmed with me that I had lost a blackberry. When I went to upgrade in december they had told me I was paying for BIS all that time. So I paid an extra R37 pm for a service I could not use in the samsung I had in store. So the sales agent sees I no longer am using a blackberry but does not remove this charge. I am due R222 in overcharges. Knowing this I stay with cell c for another 24 months and I take out a data contract. For being a loyal customer I want compensation. I want the money back that was taken from me. To top it off this month they take an amount that I was not prepeared for and calling them they tell me they realized the error and credited my account. What if that amount was not availabe. Why no call to let me jnow you slipped up. I am not happy at all. I am happy with my contracts my phones and the call centre service but store staff are unhelpful and rude and your biloing is up to no good.