HTC EVO 4g

I have been with Sprint for over 10 years and spend hours of my time on the phone with their rude customer Service people with issues with our HTC EVO phones.  We have 5 lines and 3 of them are the HTC Evo 4G phones that have never charged correctly with the chargers they come with.  They have replaced the charger and battery on 1 of them after we had to send it to the the company that handles HTC, I purchased the phone at Sprint, I pay the monthly bill to SPRINT but they state that it is not their issue we have to contact HTC. This is complete BS as the one I am having problems with is 5 months old and I was told that because I don't have the monthly insurance thru sprint there is nothing they can do. Why the hell would that insurance having anything to do with a phone that obviously has issues with their chargers as all 3 phones have the same problem.  Sprint needs to realize that customers time is a valuable as theirs and I will sue them if thats what it comes down to if I need to spend hours on the phone with them every month and deal with the most rude employees who should be lucky they have a job in this economy as truthfully with their attitudes they don't deserve the job they have!!