Dissapointed

Good day. I've recently reversed an upgrade on a phone Vodacom sent me. have sent the phone back within the window period they gave. The phone was picked up. Afterwards ,2 days later I have phoned to asked whether they have received the phone because I didn't get any confirmation of the pick-up and want to know what's happening. The lady in the after sales department Nompumolelo confirmed the next day that i have phoned, the phone is received already the system just need to be updated. She will phone me back. She never phoned and i have been calling everyday since and got told every time she will phone me back. Only to receive an sms of that my new upgrade is done with the amount due. So now i do not have the phone and got a contract I must pay for 3 years? Any advice on what to do please?