Hello & Welcome to Just Answer,
Sorry I didn't see your question earlier and to hear of any issue you are having with your phones.
To help you with this issue, may I ask:
1) How many TOTAL cordless handsets do you have with this system?
2) What phone service provider (phone company) you have for this phone line?
3) WHEN did this issue first begin?
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?