If you hear dial tone, but can't dial out. 
Please follow below to debug:

Case 1: After dialing, dial tone stop but won't make call:
    You need enter 10 digits (including area code) or press # to make call.

Case 2: After dialing, dial tone won't go away:
For some older model landline phone, the key tone may be too weak or too loud.
it requires to adjust "off hook power" to operate:

* If dial tone too loud, lower the "off hook power" by press 72# from your home phone keypad while off hook (should hear an acknowledge tone).

* If dial tone too weak, increase the "off hook power" by press 74# from your home phone keypad while off hook (should hear an acknowledge tone)

Please click here for instruction to change setting.  (set "off hook" power).

Case 3:  If incoming call's ringing ok but can't dial out, make sure your cell phone is not in sleep mode.
Some cellphone will disable Bluetooth when it went to sleep mode. Keep your cellphone power plug in and disable sleep mode.