how to leave a good customer service review?

There couldn't be a worse, more incompetent company than T-Mobile. While the people I've dealt with have all been nice and helpful, their technology has been a complete disaster for us. We had four lines for about four years, and we recently reduced it to three upon the passing of my mother. The connectivity for us in Orange County, CA with my mom in Veneta, OR was ALWAYS AWFUL - no video calls, and calls constantly getting dropped. Since reading a positive review of Consumer Cellular by Consumer Reports, we decided to switch carriers. BUT T-Mobile can't or won't UNLOCK my device. And the manager of the local T-Mobile store explained that the reason for locking it in the first place is to prevent people from being able to conveniently switch to a different carrier. EXTREMELY UNHAPPY.