Bang and Olufsen Customer Service Issues

I have a Beocom2 phone, but I am unsure of its age since it came with the house. After changing the battery, we're struggling to get it to function. The only instructional video available was not very clear. The downloaded user manual doesn't detail battery replacement either, making these phones quite complex. Another Beocom2 we have rings and seems operational, but disconnects after a minute of conversation. I've also replaced the battery in a Beocom6000 handset, but it's not charging. Among our four Beocom6000 handsets, swapping it with others didn't resolve the issue. I'm seeking assistance or advice to address these challenges with our phones. Thank you, Karen K.