Were they UK or India based the people you spoke to. I would try them again and then write to BT executive complaints -just send an ordinary letter addressed to the Chairman at BTs head office, address is on the internet under BT Plc . They know the HH5 is not all that good and say you have tried and tried and tried and that the regular customer service people wont help you.
I know writign to the Chairmant seems an over reaction but he has got teams of people working on executive level complaints and its BTs own fault fr havign such poor customer service anyway.
PB