Hello & Welcome to Just Answer,
Sorry to hear of any issue you are having with your phones.
To help you with this issue, may I ask:
1) The Model Number of the phone system you are working with? That model should be printed on a sticker on the bottom or back of the main base unit and START with KX-TG.
2) How many TOTAL cordless handsets do you have with this system, and if more than one, do ALL handsets have this issue?
3) What phone service provider (phone company) you have for this phone line?
4) If you have ANY other devices (phones, fax, alarm system, etc.) attached to this same phone line and if so, are they working properly?
5) WHEN did this issue begin, or was first noticed?