I can't comment on either service but in all honesty if you want it done properly you're going to have to go to the carrier that the phone is currently locked to and pay them to unlock it.
With that said, I gather those services basically just do that for you - they complete the unlock process with whichever company it is currently locked to on your behalf.
I do know with O2 PAYG SIMS for example you can unlock an iPhone for just £15 - you just need that amount of credit pre-loaded onto an O2 SIM in the phone to complete the process.
Hope this helps.