dissatisfaction

I am so disappointed with the customer service. I bought my sister an i-phone 8 from mobi trade, which over heated within 2 weeks after recieving it. I communicated with them, they advised for me to send it back to them, a whole week went by as I was pestering them about when I would get my phone back, eventually they answered saying it would be sent through postnet last thursday. To this day we have not received any tracking number to see how far the process is