phone claims to have sent texts but recipients do not get message, abroad

When I send a text, my phone acts as if it has successfully sent the message, but the recipient does not receive the message, and the number of texts in my allowance has not decreased. I can make phone calls, receive texts, receive calls, use internet as usual. The problem has only started since I have gone abroad (in the EU, where id mobile says texts/calls comes out of my allowance as usual). Does anyone know what the issue might be? Thanks.