Buderus Combi A6 Error Ongoing For One Year Despite Five Paid Services

For about 1 year, I have been experiencing an ongoing A6 error problem with my Buderus combi located in Hatay İskenderun. During this period, the authorized Buderus service has come to my address approximately 5 times, but the problem still has not been permanently resolved. Each time the authorized service came, a service fee was charged, yet no final solution was provided and the A6 fault continues to recur. Despite repeated visits and payments, I still cannot use my combi properly, which is both financially and morally frustrating. I request that the A6 error on my combi be completely and definitively resolved and that the service fees collected in these 5 visits without a solution be refunded.