Cell c contract went wrong.

I Latoya Cottle took out a new contract with Cell C but I am already an exciting client with them with a Sim contract,2phones I took out another contract with them wich includes2 phones for R399 wich is A35and A25 I received my phones on the 26Aug2024 I only opened it on the 27th of Aug because it was a surprise for my daughter I did not want her to see the phones so I waited till she went to school.as I was opening it on the 27th I see that it was a A55 and A25 I called them from my cell C simcard wich always has minutes to call from I could get a hold of they Call center with the number is 085 145 I was calling for that whole month with the following month of Oct to inform them of the wrong phone but as I was saying I couldn't get through to them .I had a discussion with a colleague at work in the middle of Sept than she told me no you can't call from a cell c Sim to they call center you have to call from another network never knew that so I call them and at the same time I received my statement from them as I worked out my amount that I have to pay them every month didn't correspond with the statement they have send me.usually if the phone contract is online they will call and ask do you like your device or do you like to change it or are you happy with your device no one did call to ask or to inform me they have sent the wrong phone I was the one tried calling.them for a month long but didn't succeed only after my colleague inform me about calling them from another network .so I called them and ask them why my monthly payment is so high and according to me it isn't supposed to be that high and than only they realized they locked my the wrong phone and that they gonna deduct every month the R659 and not the R499 remember I was the one calling them.to inform them about the phone and the price now they want Me to sent the phone back and my Child is already using it and are used to the phone .they want it back and send me the correct phone only now that I am questioning it so in order for me to pay the correct amount of R499 and not R659 they already deduct the R659 now I am saying to them that I am not sending the phone back it was they mistake and now they want me to rectify they mistake and they said if I am not sending it back they will continue to deduct the R659 and not the R499 but I did sign up for the deal of the R499.what do I do incase of that