I got Home Signal when I moved to Seaford early 2015 ... link is here http://support.three.co.uk/SRVS/CGI-BIN/WEBISAPI.DLL?Command=New,Kb=Mobile,Ts=Mobile,T=Article,varset_cat=signal,varset_subcat=3804,Case=obj(12975)
Similarly, we had no reception at home but 3 do a thing called 'Home Signal' which plugs into the router and provides a perfect signal all over house. It is not Wi Fi calling and I assume all service providers do something similar. Might be worth checking with yours