Superonline Sent Me Wrong SMS Then Claimed I Broke Contract

I was a Turkcell Superonline customer, and they sent me an SMS saying that my contract would end on June 30. Relying on that, I switched to TurkNet. Now, however, they’ve issued a bill of around ₺5,000, claiming that I still have seven months left on my contract. If that’s the case, why did you send a message saying it ends on June 30? When I checked the SMS section, I noticed that the message had been deleted. Superonline is clearly trying to take money from me by force. I will take this to court, but I absolutely will not pay. I’ve been a loyal customer for years, and the amount they’re demanding is more than what I’ve used in total. If you break it down by month, I haven’t even used ₺5,000 worth of service. I will pursue my rights to the end and even file a compensation lawsuit against Superonline.