Actually, its not necessarily the line quality - its how much PTCL is willing to dispense out in bandwidth from your exchange end.
That's why performance varies from exchange to exchange, and locality to locality.
For instance, PTCL in Bahria Town Rawalpindi is miles better than in the Gulrez area. And I know cause I've used them in both places.
Speed tests done on a foreign server are a bit more accurate than local speed tests. Try performing one on testmy.net and see there what you get.
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