After a week of excellent BT mobile connections, we have been plagued by "not registered on network" issues. We use top of the line Galaxy Note-4 phones, running latest android software (all up to date). Problem began out of the blue on 18 May 2017. Called and used chat to seek help. BT support repeated all the usual basic stuff - turn phone on and off, reinsert sim - like we would not have tried that first! We then asked for new sims - which duly arrived. Reactivated our new sims - no change. Eventually BT technician admitted they had no idea why our mobile signal swings wildly - 4 bars to zero bars and back within seconds. No idea either why when in our postcode RH5 6AX (Westhumble, Dorking) our phones do not display the mast connection speed (4G, 3G, H, etc) but show this in other postcodes. BT also admitted they do not handle/fix mobile mast issues. They eventually admitted 'their' masts are all managed by EE - which BT now owns. BT suggested I (myself) call EE direct. EE failed to pick up calls. So I uploaded a fault report to EE's mobile reporting site. Why does not BT show this link on mybt.com? Here is EE link which does not require login https://myaccount.ee.co.uk/networkchecker/checkservice. My fault report generated a text reply - received once I departed my postcode. After two days a new EE text reported "fault was now fixed" and to restart my phone. But no change! What to do - other than change operator? Does anyone have email address for BT head of customer services or complaints? Do they care about retail customers?