Hi, I am in the same position, yesterday whilst still the UK I opted for the roaming for the USA.
It is the £35 package for 10 days.
I’m in Florida now. anyway, arrived and I always ring home to my husband to let him know I had arrived.
Just kept getting a message, sorry no calls allowed!
I got a message saying the roaming was activated and wouldn’t interfere with the cap?
But it does! Just tried again, same thing.
Also says my next bill will be £78, now my normal monthly plan costs me £29 a month, then ID have put on the £35 for 10;days USA roaming which isn’t working. But that doesn’t come to £78.
This is bad no phone working, my husband was worried and thankfully could ring me, what is going on with this roaming?