Is valid non compete agreement clause?

[PK 2017]

I am working in Madison, WI for state client through a vendor, since last 3.5 years. I was working in model of Client -> Vendor -> sub-vendor -> My Employer -> Me (until June 2017).

 

When I joined state project 3.5 years back, my employer and me signed a non complete agreement with sub-vendor (though no agreement with main vendor) and need your suggestions to verify this agreement if this is legal and enforceable. Statement/language of "non compete agreement" is given below.

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4. Non-Competition

 

Without "Sub-Vendor name" consent, Contractor will not accept (and Contractor Company will not fill) a position of similar duties, or a position to provide substantially similar advice or consultation with any Client or entity for which the Consultant performed services for a client of "Sub-Vendor name" during Consultant's work with "Sub-Vendor name" Client and period of contract  starting from the last day of Consultant's work with that client on behalf of "Sub-Vendor name".

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I need your suggestions to verify if above non-compete agreement is legal and enforceable to me and my employer. 

 

Why they are behind me?

As per WI state policy, I can switch to any vendor after completing 3 years, as position is bound to a vendor for 3 years. When I completed 3 years in June 2017, I switched to a new vendor joining in a new position and removed extra layers (old vendor and Sub-vendor) to have a smooth H1B renewals and fulfill my financial aspects.

 

I switched to a new vendor for a new position now, however old vendor and sub-vendor keep calling/emailing me that this is a contract breach and I would face legal obligations if I not listen to them. I tried many times to settle this, however both are saying it is agreement breach.

 

Could you please provide your legal advice on above non-compete agreement clause and suggest me on next steps?