Then Mrp Mobile just had to go wrong just after lunching their sim card

I received a call on the 5th or 6th of April from Mrp mobile telling me about their promotion that they have on phones and then they offered me a phone but i told them that if its not the one that i want i will return it and the guy who was offering me this phone he said to me its OK cause i wont be paying for anything so it will be like a loss on them and i even asked for the call recording reference number and they gave me and this is the recording number mrp-***0-3. so this monday i got debited by mrp and they took R199 from my account so i called them on tuesday so this lady who was helping me said no its ok they will return it back and now today i called because she had said she will call me back but didst so when i called mrp mobile today this other lady now tells me that they wont be paying me back that money because when they came back to take the phone i signed the return slip in which i had to sign it back so that RAM could collect the phone and apparently that's why now i have to pay but i still say that they had no right to take the money because at the beginning that's not what was said they had told me that they wont going to make me pay for anything unless i take the phone and start using it since it was a promotion.