How do I disable my call waiting feature, before a call comes in? I have At&t.?

Question

It's not a cordless phone.

Answer 1

At any time, you can dial *70 i.e. Cancel Call Waiting for the next call.

Before making the call, you can dial *70, during that call, Call Waiting is disabled.

If you just dial *70, during the next call (incoming), call waiting is disabled.

During the conversation also, you can dial *70 and from that point onwards, Call Waiting is disabled.

Answer 2

I'm not aware of a way you can disable it before the call comes in, but you can while making a call by dialing *70 first, and if you receive a call, you can press flash, *70 and flash back to your conversation and it'll be turned off for that call.
-- EDIT:
I found this on AT&T's webpage, it's worth a try:

To turn on Call Forwarding, press 72# (1172 on a rotary phone). At the dial tone, enter the number you want your calls forwarded to. If the line is busy or doesn't answer, repeat the above process and it will be activated even if the line is busy.

To turn off Call Forwarding, press 73# (1173 on a rotary phone).

Answer 3

Dial *70 and then the number.