The price cap is not necessarily the issue, but can you be specific as to how you "informed" EE of your travel?
To use a pay-monthly phone abroad requires roaming to be activated, this is normally done by texting ROAMING to 150 before leaving the UK - did you do this?
Roaming enables your phone to connect to foreign networks, and without it will cause a lack of coverage abroad and thus an inability to make or receive calls, send or receive text messages or use mobile data.
If roaming is not active, your only recourse will be to contact EE CS from another means, and request it activated.
