while i do use 256k cable i have had the displeasure of using dsl... its disconnects can be a pain if you have a less than great ISP...

most ISP's have a technical support phone # which is 24/7 which can usually be found:
on the modem
on the service package pamphlet
on the bill
in the phonebook
on the website

i've had some problems with the connecting cable on the cable modem usually the problem is something so small you would even think of... in my case it was a stray grounding wire in touching the coaxial cable wire, which was my fault from when i had to re-locate the computer to the other end of the house using the same wire, i had to severe the connecter to get it through the hole in the floor then, run it to the other end of the house into a different room, then re-attach the connectors head then after a few hours of thinking about how to solve the problem i check over everything lastly the actual cable then fixed it.