non-solicitation agreement

Hi,

I'm employed with company "A" in florida on a non-solicitation contract.
I work for end client "C" in kansas having a vendor company "B" in between A and C.(basically its a C2C business)
"C" is a direct client to "B" and not to "A".
and now company "C" has given me a fulltime opportunity to work with them directly.
Vendor "B" doesnt have any problem wit this since he dont have any agreement with "C".
But my current employer "A" is saying you cannot work for "C" since you have signed non-solicitation agreement with us.
IS this agreement valid at all..? C is not a direct client to A hence i'm thinking the agreement is not valid.
Can you please help me know if this is valid or not.
Is there any possibility that company "A" can sue me?

and also i want to let you know that the non-soliciation agreement was never signed by employer and sent back to me.
it was only signed by me and i sent to them.

Thanks!!