Unlocked Motorola 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!