Mahmood,

The main reason of such internet connection deficiencies is not the Central Office fault but the cupper line(infrastructure) between your place and the CO.
You'd better check if your neighbors have such a problem, if they don't, you can request a line change from the Telco (these pairs generally dispatched in bulk quantities, so there is likely to have spares) Otherwise, to connect the Mains to line may also ruin the line itself and sacrifices the voice connection ability you have. But I am sure it appeases your nerves :o)

Rustu