Kids, by the sound of it. Jealous kids, perhaps. Jealous that they never thought of the service ID first, or jealous of your mad skillz.
If it keeps happening I'd head over to the official 343i forums and petition for a change and a reinstatement of my service ID. Just because somebody reports you doesn't mean they're being honest. And if people can't understand that, then all we can do is either stop playing, or accept that our gamertags and service ID's don't make us awesome.
Of these two routes, if we choose the latter, just go with something that's impossible to reasonably consider offensive. I mean, anybody who reports an ID of “B252” is obviously a rutting troll, and anybody with half a brain could see that.
So hang in there. Having the “cool” armor bits, or a nifty gamertag or Service ID does not make you awesome. And anybody who disagrees isn't worth taking seriously. Some of the best players I've personally gone up against had default armor and generic Service ID's because that's part of being a hustler. Get your opponents to underestimate you and they won't give you their best.
Take it easy. Have fun. Everything will be alright.