They've deactivated and removed from your account your V HD / V+ HD box (you didn't say which). If it's a V+ you should have had a letter about it being unsupported after 28th Feb. Now if you're on VIP you should have two V6 boxes, so they should be sending another one out. For the quickest resolution ring up using the method the above poster mentioned to speak to UK Customer Services/Retentions.
With regards to your broadband issue, I'd create a separate thread for that issue over here.
HD boxes ceased working at the end of the month, you should have had a letter/email about this and a V6 offered for free
Not quite, the V+ boxes won't be 'supported' after 28th Feb. The V HDs, however, will be formally withdrawn at a later date and customers with these boxes haven't yet been sent letters notifying them of withdrawal despite what some staff are saying. When the last of these boxes are withdrawn then I guess that's when the remaining V+ boxes will also completely stop working.