I changed battery and I have no dial tone - Plantronics CS55 Wireless Headset

See itf you can find someone who can try a different phone on that phone cord.
It may be a bad battery, or the phone line may be dead.
That is why I suggested you try another phone to see if a dial tone will come through that one.
If you get that dial tone on another phone, then suspicion a bad battery or battery charger.
God bless your efforts.

try changing phone to tone dialing . one phone line has been setup for Decadic dialing and the other line may be setup for tone dialing.
If tone dialing is working on one line but not the other then get phone company to change the dialing type on the phone line.
Dual tone multi frequency is the technical name for tone dialing and is more efficient than decadic dialing or pulse dialing.

Well, cannot find ia5862...but from ia5863 which must be similar; Manual at http://www.scribd.com/doc/64707312/Vtech-Phone-Ia5863-Manual-r2, it says... Set the dial mode
If you have touch tone service, the phone is ready to use as soon as the battery is charged. If you have pulse (rotary) service, you'll need to change the dial modee• Press
PROG.
• Press o runtil the screen displays
DIAL MODE:
and the current settings• Press
SELECT.
The current setting blinks • Press or to select
TONE
or
PULSE.
• Press
SELECT
to save

Hope it helps, sounds like the phone should ALREADY be on tone dial out of the box.

notify phone provider to check and test lines

The battery in the handset may be faulty/flat. If it does not charge up then replace the battery.

I would contact your phone provider. It could be a coinceidence that the dial tone stopped working.
DSL does not require dial tone to work.

That isn't a whole lot to work with. Get a working phone and take the cord out of the base of the GE and plug it into the working phone.
If the working phone gets a dial tone, look into the modular receptical on the GE base and see if the contact wires aren't out of place.
If you don't get a dial tone on the working phone, try changing the connection cord between the phone and the wall. Also look for the same problem in the wall receptical as discribed above for the GE base.

no dial tone. the handset shows "searching".

Dial tone is OK, but can't dial out
• Make sure the tone/pulse setting is programmed
correctly.
TONE/PULSE DIALING
1. Make sure the phone is OFF (not in TALK mode).
2. Use the CID/VOL left (-) or right (+) arrow button to
scroll to 1TONE or 2PULSE, or use the touch tone
pad on the handset to enter the desired setting. For
example, to choose TONE dialing, press the number 1
key. 1TONE is the default setting.
3. Press flash/program to store selection. You will hear a
confirmation tone.

Lisa, If the 900MHZ phone is Model 26928M programming for rotary dial usually goes like below, can't hurt to try on any model. TONE/PULSE DIALING This adjustment allows you to select tone (touch-tone) or pulse (rotary) mode dialing. The phone is pre-set for touch-tone use. To set to tone or pulse dialing: 1. Press and hold the program button for two seconds. You will hear a beep. 2. Press the *tone button to select Tone Dialing or press #pause to select Pulse Dialing. 3. Press the program button again. You will hear a confirmation tone.