Hello, 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.
Unfortunately, there is simply no ability to repair these units any longer.
There are no parts available, and the branch of GE that made these went out of business ages ago. They are now just a rebranded product made by generic companies.
Even if parts could be found, the cost of labor to fix it would be in the hundreds. You could buy a brand new system from a more reputable manufacturer for a fraction of that.
The new dect6 models have far superior range and clarity, and there are some special amplified and tcoil compatible models. Here is a model I'd recommend: http://amzn.to/1Qc6oR5
If you feel that one won't be loud enough, there are specialty amplified models that are further boosted: http://amzn.to/1SUx1Yd
One other option that you may consider is a used system, there is one available on ebay at the moment if you'd like to take a look at that:
I am an independent technician and I've spent my personal time, unpaid, in an effort to assist with the question for which you solicited my services. This site works on the honor system, and to that end, I have prioritized working with you ahead of other paying customers.
I am only paid for my efforts when customers such as yourself leave positive feedback for my work. Again I apologize there is not a better outcome here, though this is really beyond either of our control. I do hope you’ll consider leaving a positive rating for me, rather than “shoot the messenger”, so that I may get credit for my time spent in good faith to answer your question accurately.