Dsl Link Unstable For The Last 2 Months....

I have complained BSNL many times for unstable dsl around 5-4 days :( they only say that it will be fixed blah.. blah..
I have checked my lines and everything's good even the splitter and modem.
Line man have also changed the line and took 1000 rs from me but still no change.
Any help would be appriciated.