Test telecommunication website

I am new to testing.
If I want to test any telecommunication web-site by manual testing what are the features those should me consider?
If I want to test for
1. VOIP
2. SIP
3. forwarding call, 3 way call, call waiting ?

U should test all the features

GSM conformance testing
SAR (Specific Absorption Rate) testing
GPRS (General Packet Radio Service)testing

3-Way Calling

The 3-Way Calling feature lets you talk with two other people in one call. Use it to save time, or just have fun!

To make a 3-way call

Phone the first person and tell them you’re going to bring another participant in.
Press the receiver-disconnect (or or ) button to place them on hold.
When you hear the dial tone, call the next participant.
When the second participant answers, press the receiver-disconnect button again (or or ). All three people will be connected in one call.
3-Way Calling tips


If your telephone has a or button, use it rather than the receiver-disconnect button.
If you are unable to reach the second participant, press the receiver-disconnect button (or or ) twice to connect back with the first person you called.
If you reach a participant’s voicemail, press three times to disconnect.
As long as you remain on the line, either one of the other participants can hang up and you can continue to talk to the remaining person.
During a 3-way call, Call Waiting will not work. The caller will be routed to Voicemail.
All extension phones must be hung up in order to use 3-Way Calling.