Hi,
It is possible to contact BT online and obtain a lot of useful information as well open a complaint via My BT. When you log in using your BT ID which is your email address you registered with them and the password you chose. Once you're in go to the help section and on some of those pages a Live chat link pops up on the side, you should be able to see a link about making a complaint and once you open one, your complaint will be investigated by a complaints manager. So there are ways around not being able to speak and if you do have a disability and want a text phone, there is a text relay number to contact BT and many other companies.
So as for the spend cap, the spend cap is not for roaming. This is the case for all mobile networks.
When you use your phone abroad, it uses another network and therefore your usage isn't in real-time so there is a delay, so this why the spend cap isn't much use when it comes to roaming.
As for add ons, its very important you activate these before you leave the country and it's also important to set up your voicemail pin number so you can access while you're out there.
I think you should still question your bill with BT and maybe they could give you goodwill gesture.
Where did you travel to by the way?
BT moved my family plan to EE a few months ago and my partner just came back from Belgium and was there 3 days, EE charged £2 per day as soon as a call,message or any data was used and you could use it for as much as you wanted for the rest of the day.
There are some settings both on your device and within your BT account. You can switch of roaming altogether and set usage limits, again these are different to the caps and limits for home. Then on your device you can switch off data whilst roaming.
Anyway hope this helps, if you cant find the contact and complaint links let me know
