Wierdness with an ATT Palm centro unlock.

Hi there. So my husband and I are going to be traveling to the UK, and I purchased an unlock code for an ATT Palm Centro. I should note that we also got one for an LG Vu, which worked fine. So, we unlocked the Palm with an old (inactive) cingular SIM, and it said it was unlocked. We then put a T-mobile card in it to test it, and it was not unlocked with that card. Further weirdness, I put the Nomi-mobile card in it, and it predictably said "This sim can not be used in this phone".. expected that, since there is no UK network for it to connect with. That said, under Sim Srvs link, it has a bunch of Nomi info (not so with the T-mobile).
If I enter the unlock code with the T-mobile chip, or the Nomi chip, it says "this phone is NOT unlocked". Put the Cingular back in, and it says it is.
So I guess my question is, is there something I'm missing? Some sort of code that they are not giving me? Hubby spent 3 hours on the phone with the unlock people to no avail. The phone is not a necessity for our trip, but now I"m just curious. Can't ask AT&T, since we've never had a contract with them. The phone was a gift.

hi, it's a good post, but i am sorry i can't understand.