BlackBerry :: Using Mobile Network On 9810?

I am trying to access the internet using the Mobile Network? When I go to Manage Connections, I enable Mobile Network. On the top right it shows the internet signal, with 3-4 bars (it varies) with and H+ to the left of it. Doesn't this mean that the internet should work? So I try using the Browser, just typing in something like [URL] and I get the following message, "There is insufficient network coverage to process your request. Please try again later."I've tried it a few times and it still gives me the same message. I've made sure that Data Services is "On", and below where it says Mobile Network and Network Mode it shows: AT&T and 3G/H+ & 2G, respectively.

In the Service Status tab, it shows:

Mobile Voice
Status: Available
Connection: Mobile Nework

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When I bought the phone, the salespeople had told me the internet should be activated. I called them a few mins ago and they said the same thing. Also, just an FYI, when I connect to my WiFi network at home the internet works just fine. It's when I turn WiFi networks off, and leave Mobile Network "On" that the internet stops working.