Not answering calls / Not refunding

Nico replaced a part on the engine of my boat, without discussing it upfront with me. I learnt about it once I received the invoice. He said he used a 2nd hand part. The part he removed from my boat is still not given to me. This 2nd hand part is not working, the problem exists. He confirmed he will refund me. Up to today, he didnt refund me and nor he or Yolanda is answering my calls, sms's or emails. The service was done end March/beginning April. Invoice date is 2 April.<br> <br> A paragraph from the last email 20 May: \Since I have been dealing with you