First thing is to forget using the 07744 dial thru numbers
http://www.three.co.uk/BlobServer.srv?blobdir=ImportantDoc&blobfile=price+guide+...077442–9, 077552-5 and 0808130 070 Band 1, 090 Band 4 (per call) 25p per min
0800 / 0500 / 0808 numbers that are not on the THA list Non-geographical numbers eg 084, 087
Off-peak 1000 - 35p peak and 15p off peak. All other Pay monthly price plans and Pay As You Go 15p*........
Although not free, you could register your phone with 1899, and use their landline access number to make your calls.
It would cost you your inc minutes to call the number, and your card would be billed from 1899. Not free by any means, but cheaper than direct dialing.
However, if you choose that route, check the 1899 site first for costs, as it might be better for you to use an 0871 / 0870 access number instead, at 15p per min (3's charge).
It would appear that 3 have done their best to shut down the way to make cheap calls.
By the way, were you aware it costs your family etc almost 25p per min to call you from a BT landline, which is almost 50% more than to most networks?