Claiming money from a debtor after leaving the UAE to his country

My debtor took cash and purchased his personal flight tickets by my credit cards and went back to Ireland.

The total amount is 5000€, and I only have the Whatsapp message to prove that he agreed that he owes me 5000€.

He failed to return me money for 7 months. He agreed to return me money on 26th of June, but he failed again.

Afterwards, he is not responding to any text or calls regarding paying the debt. He even threatens me to report me to the police because I try to contact him and his family regarding this issue.

Should I send him a letter as before legal action?

However, I don’t know his address in Ireland. I only found his company’s contact and address.

Should I contact his company regarding his debt issue?