Cricket locked my already unlocked phone. why?

I had bought a unlocked phone for my brother in-law, took it to cricket who I had already had service with. I added him to my plan in January of 2023. I switched plans on 4-19-23 due to needing to get WIFI in my home. I went to put my brother in-laws phone on the new plan and we couldn't get any service. contacted crickets customer service via phone and they told me I had to have his phone in-service for 6 months. It is in my understanding that the 6 months is if you buy the phone through cricket which I did not. Now with that being said if cricket just locks peoples unlocked phones that is a legal issue and needs to be resolved. I will file for a lawsuit if you guys do not unlock my brother in-laws phone sometime soon.