I have a blackberry tour on verizon but when i put my tmobile sim in ....?

Verizon and T-Mobile are two different companies that use two different technologies. T-Mobile uses GSM, which is used around the world, and Verizon uses CDMA, limited around the world. The Verizon Blackberry Tour is a world phone, but is only made to use Verizon Wireless network; therefore, problems may occur when you use a different sim card made by the GSM cellphone provider. Another thing I like to add is Verizon doesn't use sim cards on majority of their phones as well as Sprint, so the Sim Cards that they use in their blackberries are specially made to work on their network in the USA, but use the GSM and CDMA networks outside of the USA which is why its called a world phone.