Pawn in the game of 02 and BT

for the past 4 weeks i have been getting constant disconnections on my line. We eliminated every possible factor which might be affecting it, interference, modem, filters, wires, socket etc.. but still yet to find a solution. So we phoned O2 and they got an engineer round who changed the socket...problem kept happening. Another engineer came round and changed the line at the exchange and changed the junction box...problem kept happening. ANOTHER engineer came round and did another hawk test which came out fine and yet the problem still persists! This engineer empathized with us as we have had no internet for 4 weeks! He told us that there is nothing he can do as the hawk test showed no faults and that he couldn't possibly know where the fault is as all of the procedures had been done. Now as he empathized with us, he actually phoned o2 on loudspeaker in front of us to see what they say, now o2 had been saying that they will do the same thing that they have been telling us for 4 weeks...monitoring the line. Now we dont know if this is a problem with o2 or BT but we find it extremely unfair that we have been paying for no service and have a problem that is claimed to be unfixable. Has anyone got a clue what we should do? we are so stuck and need some help. thanx