[Asterisk-Users] How do i transfer/forward a call out?

[Time Bandit]

> [cellphone] 
> 
> exten => s,1,Flash 
> 
> exten => s,2,Dial,Zap/2/9729796243 
> 
> exten => s,4,Congestion 

I never done this, but I believe you are missing a final part.

If you do the same thing on a regular phone, the scenario would be this :
1- you are connected with the remote person
2- you hit Flash and get a dialtone
3- you dial the number you want to reach and get connected
4- you hangup the line and both remote are connected to eachother

so you need to change your dialplan like this

[cellphone] 
exten => s,1,Flash 
exten => s,2,Dial,Zap/2/9729796243 
exten => s,3,Hangup

I never used this so maybe I miss a step, maybe you have to flash
again before you do the hangup. Can't test it as I don't have 3-way
calling on my phoneline

b.t.w.: You had a wrong sequence in there, 1-2-4... missing the 3

hth