Re: New to Blackberry 9900
BBOS is the legacy OS, versions 7 and before. BB10 is the current OS on the Z10, Q10, etc.
As I say, the old OS requires a BlackBerry data plan. For you it would be BIS. The BB10 models do not require a BlackBerry data plan. If you have BIS on your line you will have BlackBerry data services with the BBOS model. The BB10 model may work fine with BIS, even though it won't use it, but there is a chance there will be problems. Some people had problems and turned out they had BIS, and the problems went away when BIS was changed to regular data plan.
Your carrier may not have put BIS on your line, or there may have been some glitch. The first thing to do is consult with your carrier and find out. Have them push service books. You will need to have your 9900 turned on, with the SIM installed, and you need to have a good signal.
Again, I don't know what problems you may encounter with using a BBOS and BB10 model on the same line, if that is what you are doing. See what others say on that. You may just have to find out.