If you are upgrading from a recent version of galaxy S phones, do not swap the sim from your older phone into the S-10. It will fit and work, but, apparently they are internal differences that might constrain the S-10's capabilities. Have received this information from a few sources including AT&T tech.
PS since this information was verified by AT&T tech I don't blame you if you question it.
PS since this information was verified by AT&T tech I don't blame you if you question it.