I was having difficulty with my (old) BT Easicom 1000, when incoming callers could hear me, but I could not hear them. I Googled to find a replacement, as fault report told me that it had probably reached the end of its life. NOT TRUE !!
Whilst trawling through phones for sale, I happened upon this Community questions page. MANY THANKS to the correspondent who asked whether the questioner had changed the batteries (4 x AA) in the base. I had no idea that the batteries were there, as I did not have a User Manual. I am absolutely delighted that replacement batteries have cured the fault. Well done - you have saved me quite a sum of money !