Hello TaraLV,
We understand you're getting a poor signal on your iPhone and it's causing problems with phone calls. We know how important it can be to get good service while on a call. We'd like to help you get to the bottom of this.
First I recommend removing any case, protective sleeve, or other accessory you have on or connected to your iPhone and then testing to see if the issue still occurs. If it does, try out the troubleshooting steps listed here: If you can't make or receive calls on your iPhone. Those steps should help you narrow down the issue further, and may help resolve it as well.
Thanks for using Apple Support Communities.
Take care.