Many times! I bought a new modem once and I had to call my ISP (comcast) so that it could be registered. Of course, this meant at least 15 minutes in hold until they could get me to the people in charge of this. When we finally did this, they had to enter the MAC and serial numbers... However, all in all it took about 5 attempts to register the modem. Figuring it was 15 min hold for each 15 x 5 = 75 min plus the attempts, about 10 minutes trying to get it to work each time 75 + 50 = 125 minutes... 2 hours... I feel your pain friend.
depending on where you live, the consumer protection services could be a great help. as many people have these issues, and many remain unresolved unless you buy or rent new hardware from your ISP. depending on your contract and the amount of other people having issues, you may be able to submit a complaint or notification to the consumer protection agency in your state, and the company involved would have to address the problem on a wide-scale basis. tho the difficult part is the fact that it would probably go to court before any resolutions are made, so it would take a lot of time to address the issue. If its something that you have problems with on a regular basis, it may be a unrelated hardware issue such as wireless connectivity problems, or a faulty line to the isp box. most companies dont want to take the time or effort to address the issues properly, and offer a more expensive (for the consumer) solution to the problem so they are paid for fixing something they should have properly installed/ maintained themselves