I don't really have strong enough lte here to use voip over data. I have a google voice number and I have it set to forward calls to my cell number. If I am on wifi I answer it with grooveip, if I am on cell data grooveip turns off and it just goes straight to my real cell number.
The only real downside is that when it comes in on wifi there is a little delay when I answer as technically both dialers are ringing but the grooveip dialer supercedes the cell dialer. An inelegant but effective solution.
I pretty much just give out my google voice number for business things as it accepts both calls and texts and I use my real cell with friends since they are the ones sending me mms which doesn't work with gvoice.