Cordless answerphone (Corfe Mullen BH21)

Gigaset 620A answerphone base plus extra handset. Answerphone in good working order, handsets OK for outgoing calls but temperamental with incoming. Maybe new batteries,spare or repair, just use answer phone for incoming calls then ring back caller?,extension phone for garage/ summerhouse/garden shed?? Several possibilities if you can cope with unreliability!! All cables and chargers and set up instructions included. Fair Offer Policy applies