Turkish Airlines Rejected Compensation for Delayed Flight

Unfortunately, the aircraft I was on with Turkish Airlines (THY) was delayed for a total of 5 hours. Because of the long wait, I missed my connection and had to make other arrangements. They tried to make things right by offering me a certificate for a free item. When I tried to redeem the certificate for 100 euros at their office in Istanbul Airport, I was told that they were unable to do so. My frustration is mounting, to put it mildly, after waiting for so long, I'll have to deal with yet another obstacle before I can collect the compensation I was promised. The office employees let me know they lacked the resources to complete the task, which was both disheartening and disrespectful. I feel even more disappointed and upset about the situation after this...crossing my fingers that Turkish Airlines would listen to its customers' complaints about these kinds of delays and start compensating them fairly and without further ado. Does anyone have trouble being compensated for flying delays? It would be helpful to hear your thoughts and advice on how to handle similar situations.