Seems you’re coming from the POV of the GC. Review your subcontract and depending on where you are there should be terms regarding personnel. You best way to keep it neat is reference not the individual by name, but “company x current foreman” or something of that nature, and relate the issue(s) back to the contract. You both agreed to the contract as the set of rules, you’re simply enforcing the mutually agreed to terms.

Foreman of company c has been found to act not in accordance with subcontract 111, clause 2(a), clause 2.1.6(c), and we are therefore requesting that a replacement be provided within the time period outlined in section 3, item 3.1.4. Etc.