The DSL service is not the problem itself, there are number of facts evolve which majority of peoples ignore it:
1 - The telephone line
Even though it's not the consumer fault, but in order to get the maximum quality service from your DSL, just goto your nearest telephone exchange contact a lineman, give him RS 200 and tell him to add a ethernet cable directly from the telephone pole to your house (of course you have to provide him a ethernet cable) and then you can use that cable to connected your ADSL modem, the main reason for using the ethernet cable is getting lower resistance = maximum signals.
2 - Wrong Placement of Splitter
I saw few various peoples who placed the splitter after the telephone distribution point in their homes (a distribution point can be a telephone set too) which is wrong, and your DSL will keeps on getting DC! always place your splitter at the main distribution point and then distribute all the connections after the splitter to your other phone sets and ADSL modem.
3 - Distance from the telephone exchange
DSL is a service which is very sensitive when it's comes to the distance/length factor! make sure your home is not more then 2KM far from the telephone exchange of your area, else you will always have the problems, many peoples don't consider this point, but it's the most important factor.
4 - Telephone Exchange:
Unfortunately not all the PTCL telephone exchanges have a dedicated staff, some of the telephone exchanges contains the "Hadaram/jahil" staff which don't maintain the service within the telephone exchange! usually small areas exchanges fall under this category.
5 - Service Fault:
It's true that sometimes PTCL DSL service do gives the problem, but it's due to the reason that these days they are testing the new services like IPTV etc, furthermore you will get worst service on weekend, becasue on weekend the whole telephone network remains busy due to lots of load on the exchanges, in that case none of the DSL service can give you a good service as all the DSL service provider utilize the PTCL telephone network
I hope the above information helps a bit.