A beeping BT Freelance XD550 base means the base is faulty and you need to buy a replacement.
You can buy a replacement BT Freelance XD5500 base from sellers on eBay for £3.99 for the base and £3.99 postage & packing..
Upon purchase you need to reset the base by following the instructions below:-
BT Freelance XD 5500
Resetting the base & handset/s on a BT Freelance XD5500:
Hold the Find button on the base unit until you get a double beep then
tap the Find button 7 times.
On the handset:
remove a battery
hold the menu key and refit the battery
screen says SW VERSION
press up arrow key until screen shows REGISTER CLEAR
press menu again and wait for OK to appear
remove a battery and refit
Registering the XD5500 handset.
Then register the handset to the base as follows:
Hold Find button on base unit until you get two beeps
Scroll to register
Scroll to Register Base
When it says PIN ? Enter 0 0 0 0 (four zeros) and press menu.
If you have more than one handset then repeat registering the handset to the base for each subsequent handset/phone.
If this procedure fails to solve the issue, then you have a unit with a fault and if it is less than a year since purchase the retailer should change it for you.