More airtime credit on the network/s - UK

[VincentAnoid]

I've heard of that trick you can do that apparently gives you more airtime. It is where you phone the top up line from several phones all at once, all on the same network. Entering the E-voucher on all of the phones and then hitting the # or * (What ever button it is to confirm) all at the same time. That apparently applies credit to all of the phones.

Not sure if this really works or if it no longer works, has anyone had any experience with this?