, I’m Nathan, and I’ll be assisting you today. My livelihood depends on your positive feedback, so your satisfaction is my highest priority.
Sorry to hear you’re having trouble.I would agree that based on what you described, you've got a bad handset. Just to be safe though, in case you purchased an incorrect (or faulty) battery, it would be worth swapping the battery in this handset with another working handset, to see if the issue stays with the "bad" handset or follows to the other, confirming if the handset was faulty or if it was a battery issue.
If it does need to be replaced, you need the C59H handset model,
Though you don't actually need it, it may be more economical to buy a new system. You can get a new base station with 1 handset than the cost of a replacement handset. You'd just pair the new handset to the existing system, and you could tuck the new base away in storage in case the original ever fails, then you'd be able to have longer term use of your system.