How can I stop my Xbox from disconnecting randomly?

This will be my last request concerning this problem, since I am far fed up with worthless Xbox servers and crappy modems or whatever. I've called in to my ISP multiple times regarding my frequent drops while I play my Xbox or browse the web on my laptop. It was only until yesterday that they told me my internet had dropped 10,644 times in 2 months. A guy came out, did some stuff, and everything seemed fine. I can actually see a difference. Now though, I still cant play Black Ops Zombies on my Xbox and get to a high round because every time I get past round 35 I lag like f**k and 2 secs later, phones out, wireless is out, Xbox is out, and its all back on 15 min later. So here's the last questions I'll ask: Should I just get a better ISP or something? Is it Microsoft's fault? Treyarch's? Someone please just end this already. I'm sure there's a metal bat somewhere in my garage and I don't want to use it on this junk in the corner called a "modem". Also: I get dropped frequently with Black Ops since it's my only game, yet I'm sure this has happened with other games as well; Categories seemed sketchy too, since this problem is with everything. So sorry if this isn't placed properly.