Technically yes... you ca get the Hub2 reactivated onto you account but you will have to cancel the 1GB upgrade and go back to the 250 package.
How easy it will be to convince them to do that is anyone's guess. Depends how long since the upgrade as to whether you can do that penalty free.
But if the Hub5 is dropping when in modem mode (is that correct?) there may be either a known fault or a problem on your connection.
Check for any “known network faults first - Try in 2 places and report back
1) Try the “check service,”Area status webpage" (link at top right of this forum)
2) Then also try the “free & automated” Service Status number - 0800 561 0061 - which usually gives the most up to date info. and tells you of more local issues down to street cab/ postcode level.
I do not work for VM. My services: HD TV on VIP (+ Sky Sports & Movies & BT sport), x3 V6 boxes (1 wired, 1 WiFi, 1 on PA) Hub5 in modem mode with Apple Airport Extreme Router +2 Airport Express's. On 250Mbps, Talk Anytime Phone, x2 Mobile SIM only iPhones.