Debt collection & restrictive convenant appraisal

Hi - I have a one man band training company working with disadvantaged groups supporting them into employment. My company contracts with another CIC that is currently refusing to pay me any money that it owes me. I have an invoice that is 4 months late and am being fobbed up continually. The owner claims i have breached the restrictive covenant but i disagree and believe we are not in dispute. I would like someone to represent me to collect the debt and also to take a look at the restrictive covenant and tell me what they think of it. I have attached the covenant below. I hope someone can help me collect the monies due.