employment agreement (a bit OT)

[kans]

I am employed by an employer A who sponsored my h1 visa. Through my friends I got an contract position in a company C through another employer B. Since H1 visas were over by that time, and I couldnt get a new one with B, I hooked up employer A with employer B. Now C pays B, B pays A, and A pays me. employer A did not spend effort, no money (relocation/cash advance) to find the client C. Now C wants to take me on a permanent position, and C convinced B to agree to it. B agreed to it, and did not take any money for it. when I was all set to join C, A comes up and says I cannot join, if I do I will breach their employment contract, and they will sue me. I have worked for more than 6 months, and I feel this is totally unjustified, because the money they made, will more than offset for the h1 fee they paid by more than 10 times(I paid the 1000$ premium processing fee and h1 processing fee is prettymuch all they paid for). The employment agreement states I should not join "employers client for whom employee has rendered services while employed by employer". Since B is paying A for the work I do, would it be correct to say "B is A's client" and not C, since B does not involve directly with C, and C doesnt even know A exists. Has anybody gone through similar situation? Can A sue me over this? I was working for A, now I want to move on, how does it matter to A whether I join C or anywhere, since they did not find me the client? Any help would be greatly appreciated.