Network signal in a well insulated house

[Foxcherrett]

We've recently moved into an old Victorian stone walled house, which we completely renovated, and fitted thick insulation boards on all external walls. Whilst this is excellent for heat retention, and very eco friendly, it appears to have reduced our O2 phone signal to virtually zero! To make or receive calls, we are having to resort to our driveway or rear garden, which isn't too much of a problem at this time of the year, but in the height of winter, isn't so appealing! Is there any way we can boost our network signal?  

[MI5 · Accepted solution]

@Foxcherrett 

Only option is wifi calling https://www.o2.co.uk/connectivity/wifi-and-4g-calling

[Foxcherrett]

My wife and I are both on O2 PAY Monthly contracts, but since recently moving house, our mobile signal is almost non existent inside the house, due to thick insulation on the external stone walls. We both activated WIFI Calling on the O2 App, however this doesn't appear to have made any difference? Are there any other solutions, or signal boosters we could consider, to save us having to venture into our garden to make or receive calls?