Stay away from the Blackbery Z10 if you need to use a prepaid SIM or want to use use a local SIM when traveling. The Blackbery OS10 will lock the APN and you wion't have data. Voice and text seem to work okay.
Buy the Z10 if you are on the monthy plan or will not be traveling with the phone or you don't care about data.
If you travel a lot and want to switch SIMs then I would recommend the Samsung or Apple phones