Phone (gps/signal) just not working after being underground

[rich12]

I'm really struggling with this to find out if it's the phone or the network but basically whenever I go somewhere that has no ability of signal (train into London or an underground car park) my phone just won't work for ages.

It shows I have signal when I come back out but nothing I do resolves it and it just takes ages to start working again.

Example, went into London yesterday and as I was coming out of bond Street, my phone showed the signal bars again but I couldnt call anyone, my maps weren't working and Internet would load.
Tried to do airplane mode, restart the phone and just turn it off but nothing. Took about half an hour to work again.

Another Time was in park lane car park and once I had come back out, same thing.

Anyone ever had this before?
Phone is a Samsung s10+ and on the crappy three network.

[alorotom]

If you drop into airplane mode momentarily does this not force it to reconnect?

[rich12]

I thought it would which is why it's always the first thing I do but absolutely nothing works.

[sunbeam alpine]

I has something similar a couple of years back. Ended up swapping the SIM card and that sorted it.

[959]

A master reset fixed the connection problems with my samsung to 3