modem keeps resetting

In the past 2 hrs, my modem has reset 6+ times, this happens daily over the past 5-6 months. Ive had a tech out twice, the other 2 times were no shows. they replaced spiltters, cables, modem, told me I needed a new router (the old one was only 6 months old) so I got a new router, they switched out the old modem to a phone line modem. I just need this fixed. Anyone else have this issue and did it get resolved? I work and study from home online and need to get some work done. Meanwhile my phone is eating up data like crazy, because I think I'm on wifi, but not :/