Unresolved Daikin Combi Boiler Repair Complaint

Hi there! I want to file a complaint against Gülsoy Teknik, the authorized service provider for Daikin in Döşemealtı/Antalya. For the last three months, despite multiple calls and repair requests for a faulty combi boiler (not heating water), they have come over several times but have been unable to resolve the problem. On each visit, they have asked for payment for various reasons. We spent ₺4800 on a component known as the "expansion tank," but the issue resurfaced within a week. We've been facing chilly days with no hot water for our two kids at home in the winter. They have ceased all communication with us. This behavior is dishonest and misleading.