SMS or MMS really big problem

Hey everyone!

I have an unlocked iPhone 5 which was bought in the UK (I am in Portugal) and everytime I try to send a SMS or MMS to a group of people it changes my contacts to add a +44 to their numbers and therefore I pay for them as if they were international contacts. This does not happen if I send a SMS or MMS to only one of my contacts.

Can anyone help me with this? I can't find anything wrong in the settings. 😐