Turkcell Changed My Billing Date Without Permission and Cut My Contract Short

I switched to Turkcell with my line number 545280***49 on March 20. My first bill was issued on April 10, marking the end of the first month of my contract. The second bill was issued on May 10, completing the second month. Strangely, a billing cycle change request was made through the Turkcell app on May 11 at around 12:40 a.m., and a new bill was issued on May 20, making it appear as though the third month of my contract had already passed. I do not have a fixed internet connection at home, and I always turn off my mobile data before sleeping. I filed a complaint with Turkcell customer service, stating that I did not make this request and asked for it to be canceled, but they persistently refused. I have screenshots from the Turkcell app showing my transaction history and bills. I had no reason to request a billing cycle change, and I don't know who would think of doing that just one hour after the bill was issued—especially around 1 a.m. Changing the billing date to make it seem like my contract ended a month earlier is not a fair practice. I hope this mistake is corrected as soon as possible.