Warranty phone return

I purchased a used phone from Fizz about 6 weeks ago. 2 weeks later , the phone stopped charging and then completly shutted down and never restarted again. I send back the phone using the phone return process. And since then nothing. No news. It's been 4 weeks that I hace returned the phone and I have nothing. On the tracking it appears the phone was delivered. I don't have a phone since then and they completly don't care about it . In 4 weeks I was just able to reach the customer service 3 times. The 1st time the agent said she will track it and call me back. I never received a call back. The 2nd and 3rd time, the discussion has been shutted down and the rest of the time , I am appearing very far in the queue to talk to an agnet and the chat closes itself. I don't understand. Does anyone knows how I can talk the customer service?. Thank you.