Go to settings, phone, dial assist and try changing that from on to off or vice versa.
I have it off, and save all my contacts in international format (+, country code, number). All my calls go through like that. When dialling manually, if calling in the country I am currently in, I can dial in local or international format (i.e. in London I could dial either 020 7123 4567 or +44 20 7123 4567) and it works. For calling anywhere else, include back to North America, I have to dial in international format.
When I turn dial assist on, I start having problems.