Unfortunately, for a system this age, repairs are simply not feasible.
Few repair shops will even touch a consumer grade cordless phone like this in the first place.
The vtech brand is at the bottom of the quality spectrum as well, and this set is far past its service life, it is a wonder it has lasted this long. There are no parts available for them, and labor costs alone would cost you 3x as much as you'd spend to simply replace the entire system.
What you could do is buy a replacement handset, but the costs for these, even used, is excessive and would still be better off buying a whole new system for little more. Here is a repalcement handset: http://amzn.to/1PvZaXy
Here is a replacement system I'd recommend: http://amzn.to/1PvZzJz
IF you'd still wish to pursue repairs (expect to spend at least $125), let me know and I'll investigate local shops for you.
I am an independent technician and I've spent my personal time, unpaid, in a good faith effort to assist with the question for which you solicited my services. 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.