Unlocked V551 from Canada not getting service from most nets in Germany

Hi. I have just relocated from Canada to Germany for a year. I brought my Canadian cell phone with me, a Motorola V551. At first, it was locked, but someone unlocked it for me. It will now accept any SIM card, but afterwards I get "No Service" or "Emergency Only" from almost all providers; the same cards work fine in other phones. So far, this phone has only gotten network service under Vodafone and T-Mobile. I don't want to use them, since their pay-as-you-go rates are very high. Does anyone have an idea why this is happening? Thanks!