Persuing nonpayment of a freelancer invoice

I worked for a Canadian Production Team last year. The Production was put on hold & I was asked combine my last 2 invoices, (1 of which had already been submitted & was due for payment). Since October 2024, they have made excuses about the accounts with the funder. This week they have told me I need to pursue the funder, but the funder is telling me my contract is with the production company. I am owed £4,200. What can I do?