Hi, I have a 9900, now one of the service providers here are launching their "4g" service and claims to access it we have to subscribe to it specifically even if we already have an unlimited bb service with a 4G enable device.
Yes, they can. In order to use a data provider, your device needs to register on the service. If you don't pay for the access, they can block you. Just like if you don't pay for your basic data service, they don't allow access to it.
Which "4G" are they offering? The 9900 only has HSPA+. That's really the faster 3G that they called 4G simply for marketing. If it's LTE 4G, then it won't matter. The 9900 doesn't do LTE, period.