No Service

Good morning my name is Jody and I currently have an used iPhone 8 and for some reason my phone says that I have no service even though I have been paying all my bills. Sometimes it says no service and switches to boost for a while but I’ve had this Problem for about a week now. I have tried many things but none seem to work and when I turn off my phone it always has a boot loop problem and has hard time turning on. I believe this has also affected my battery in some of ay because my battery is draining really fast. For example before I got to sleep I always charge my phone to 100% and when I wake up it’s on 5% and that has been happening around the same time as my no service problem. If you can please reach out to me and I would really appreciate it. Thank you!