An excellent suggestion BJ: I doubt that jagga303 could expect to find anything cheaper than 2 ppm for calling 0872 numbers, if he wants to do so a lot.
However, even if he wants to call 0872s by the bucket load, I have to wonder how long T-Mobile would allow a SIM only contract to run - if it was making a loss of at least 8p for every minute of the 900 ?
For more moderate use, why not use the 03 and 0845 topup service ?
According to Mikael's post, reply #478
here, 0872 numbers can be called for 6 units per minute ( the same as for 0871 and 0873 numbers. )