retrieve owed money

I'm looking for help with recovering a sum of money that I am owed, £5,000. I have only verbal agreements as evidence, so I'm looking for someone to help negotiate and settle this debt. I need someone skilled in recovering money for people in my situation, of people with differing nationalities (I am based in Brazil with British nationality and the person who owes me is Peruvian) who can help me get the repayment that I'm owed.