Turkcell Calls to Other Networks Have No Ring Sound Until the Call Is Answered

I've been having a problem with Turkcell's GSM service when I try to call numbers on other networks. When I make a call, I don’t hear the ringing until the other person picks up, so I can’t tell if the call is going through or not. I contacted Turkcell about this, but they’re not recognising that it’s a bigger problem. They told me to send in my phone for service, but that doesn’t make sense since other people have the same problem. I’ve always counted on Turkcell for dependable service, but this ongoing issue and the absence of genuine support are really starting to get frustrating. I hope they take care of this soon.