Help please!

I’m not sure what to do here: I got a mighty last year and have probably returned it 9 times. It worked well for three months and then stopped heating up at 365 degrees. I get a few good rips and it stops heating. Each one they send me has the same problem. They won’t refund me and I asked if they could send a different product and I’d pay the difference but they said no. I’m at my wits end.