you need to check yoursel here http://ee.co.uk/ee-and-me/network/4gee/network-status-checker
as Bt mobile use the EE network then if EE show everything ok then BT Mobile will be ok - just checked and BT Mobile show no network problems
do you have a neighbour or friend on EE who can check and see if their mobile signal is ok?
So it is not a bt mobile problem but an EE network problem
I dont know what model of mobile you and your wife are suing.
Within the handsets functionlality there will be "Settings"; I would suggest you take out the sim cards for 30 minutes so any previous/redundant cahe is then lost. Having thus re-inserted the sim card[s], from within "Setting" do a networl sweep and select BT Mobile [or if it does not appear EE] and selct tat as you preferred network. Be aware of course, that other mobile providers [now] uise EE, Virgin, Orange and T-Mobile. Make sure that the dwo devices have selected BT/EE as the preferred network.
Other than that, report it to BT, grit your teeth and I have to say I've been there with stories from my network provider of twigs on trees getting in the way of the mobile signal which was hard advice to take.
[To strengthen the case of your phone call, there are plenty of apps [e.g. on Android Kaibits available to check the signal you are receiving on your device[s]. You could provide BT mobile with a date/time stmap record of mobile signal dependant upon location, time, date etc which would alow them to check your location in mnore detail.
My problem with this, came.....and then went