Persistent Problems with Infinix Note 12, Freezing, Lagging, Contacts Get Deleted

I bought the Infinix Note 12 phone about 3 months ago from Vatan, hoping to have a great experience with it. But in this short time, I've had a bunch of issues with it, so I had to send it in for repairs twice. I've been having some problems with my phone lately. It keeps freezing and lagging, and every time it restarts, my contacts get deleted. I thought that the service would fix these ongoing problems. Unfortunately, even though I've tried to fix it multiple times, my device still has the same issues. It looks like neither the Vatan store nor the Infinix company has fully taken responsibility for fixing the ongoing problems. So basically, I'm really upset and frustrated because I'm the one dealing with all the consequences. Given what's been happening, I feel like I need to do more if my worries aren't addressed, as a last resort I'm gonna sue Vatan and Infinix.