It probably isn't the ISP, but a faulty modem, cabling, lines or improper setup (possibly on their part as well).
Just as a heads up, you're going to really want to check any manuals or documentation they provide - All ISPs are different. Many cable providers are DHCP (automatic) and get you online right away. Sometimes they require you enter your account number before you can begin using a setup utility.
While many are DCHP, some DSL services are PPPOE which requires a username and password. If you aren't putting in this information, that could be an issue too.
I've seen lots of Internet problems related to lines. One family cut a dedicated line which run to the telco box... Another customer didn't pay their ISP bill. :haha: They had no idea why they didn't have Internet.. hehe! There was another scenario where downed power lines interrupted phone service for an area of town, but when they repaired the lines, at least a few blocks of people were no longer able to access their DSL. Go figure!
The point is that these kinds of problems aren't uncommon and you should consult your ISP and/or cable/phone company for some troubleshooting before you smash a face-sized dent in your desk. If you have documentation or more details on your service (Like what company, DSL.. cable...?) then maybe we can help you out.