Android phone won't send or receive texts on wifi

I don't get cell reception in my house, except for one spot next to a window. I use wifi to connect, but I'm having problems. Android phone.

1. Making calls: I can't start wifi calls unless I'm standing in the one spot where I get a teeny bit of reception (1 bar) - it's not enough reception to make a call without wifi. If I try to make a wifi call anywhere else in the house, my phone refuses to start the call, and I get an error message saying my phone isn't registered on any network and so I can't make a call. If I stand in the one spot and start the call, it goes through, and I can walk around the house and talk. I don't know if I'm also missing wifi calls when the phone isn't in exactly the right spot. 

2. Texting:  The phone won't send or receive text messages  when on wifi unless I'm in that one spot in the house where I get a bit of cell reception.  If I try to send it just says "pending" forever until the phone's in the right spot. Also, when I'm in the right spot, all of a sudden I'll get a bunch of texts that haven't been coming in while the phone's with me in other parts of the house. 

What's going on and how can I fix it? Wifi is working fine, all my other devices connect and function correctly on this network. 

Re: Android phone won't send or receive texts on wifi
Customer Service Rep

Hi there. We would be happy to help you with your service concern. We most certainly want you to have the best service at all times. Please private message us for further assistance.