I would not say that i am lucky rather i would say i escalated the problem to the right people. Do some google search ... may be linked in search .. try and find the right people... write a strong yet polite email. Post your comments on FB... Do the due diligence.. and i am sure u will get your problem resolved.
Yes you are right....i followed just same way as yours...I also wrote mail in the same way as you wrote politely and strongly mentioned my all the problems precisely. Still they were not ready to replace my box...BUT BUT BUT>>>>
I was lucky enough that my old problems those were occuring frequently so till now never been lucky enough to show my problems to engineer. but today engineer was abt to come within 30 min, and certainly i got all the problems (No Signal issue due to STB and STB can't on from standby mode) so i didn't switched off my STB and kept on until engineer came and showed him all issues so he believed my probs. and changed My STB finally....i was trying it for 2 mths but never been able to show the problems as problems were frequent.

