I have the 508. Can I use Callcentric for 2 phone numbers and Google Voice for 2 other numbers on the same device simply by choosing? If so how?
Yes, all the 8 SPs are independently programmable. Any permutation of 1 to 8 SPs and 1 to 8 different ITSPs.
If you know how to configure 1 SP you know how to configure the rest.
I did not know that it is possible to use 2 providers at the same time ;D