Like so:
- Disconnect from the internet, turn your router/modem off.
- Remove the ADSL filter.
- Pick up the phone, and listen to your line for a good 10 minutes or so. You're listening for cracking and such. If you hear cracking, then you can safely request a house call.
- Follow your telephone line as best you can, look for situations where it can be bumped or interfered with or is sagging more than those lines usually do.
- Finally, guess how far away the line is from the exchange. If the distance is bordering on 4km's away, then it's simply the distance from the exchange that is the problem.
There is no solution to the distance problem, unless there's an exchange closer to you that you can use.
If you can point the techie in the right direction, he will solve the problem.
But, the distance problem is an aspect of ADSL that cannot be overcome.
Cracking indicates a bad connection.