We have the exact same problem for the last 6 months or so. Have spoken to BT on numerous occasions. They test the hub and the connection and say there is no problem. Have been told that BT do advertise that they can't guarantee connection to mobile devices. According to BT there is nothing more they can do and we have to wait until contract ends April 2019 to move to another provider.
Can you post stats from your hub
if hh6 have you turned off smart setup?
have you split the networks?
split networks unless SH2 http://bt.custhelp.com/app/answers/detail/a_id/56419/~/how-do-i-split-my-bt-hubs-ssid-%28wireless-ne...
Well BT Engineer called today at our request but doesn't deal with Hub problems, only wiring! My Superfast fibre speed was slower than both my neighbours copper connections. It seems that when electrician rewired house he also ignored request to leave phone lines alone! Eng. rewired my Alarm connection & removed unused phone points & speed has gone up to 25+Mbs.
Phoned computer shop who remotely accessed my Desktop, updated 1 of 2 Drivers (Realtek PCle FE Family Controller which seems to have sorted Wireless connection but still very frequent drop off when on Ethernet!? Couldn't locate but suggested it's a hub setting somewhere so guess I'll have to telephone BT techies for help. Also 6month old BT wifi Extender 1200 has stopped connecting on both 2.4Ghz & 5Ghz frequencies so this upgrade, although now faster, has had major side effects & £ costs. Not sure it was worth it all in all!
it would help forum members help you if you posted hub stats - if hh6 then advanced settings then technical log information - and also enter your phone number and post results remember delete number
https://www.dslchecker.bt.com/adsl/adslchecker.welcome
Not sure I even understood your reply let alone do it! Your link takes me broadband to available locally? Doesn't make any sense to me so I've taken a screenshot of my Networks & hope perhaps that helps. I could also, I think, post a copy of a "Network log" (with Ping tests etc) or something like that.???
Sorry but only half screenshot seems to have come out!?
if you use dslchecker link with phone number it will show what is available and speed range
hub stats are advanced setting then technical log information