A transfer from a Laptop deal to a normal contract is not as simple as a tariff transfer from a T&C point of view when the contract was taken.
Different rules apply to contracts that include phones than ones that include laptops, such as lowering the tariff after a set period, technical support and R&R.
A person could take a laptop deal for 24 months, swap to mobile phone contract the next month, wait 9 months then call o2 and start lowering the tariff month after month as changing them to a mobile phone tariff would mean they would fall under mobile phone T&C's, not the original laptop T&C'S. This would not be possible on a Laptop deal contract as o2 make you stay on the same pricing band for the length of the contract as when you took out the contract.
This means you get the laptop at less than the rate you were meant to as o2 get back the money for the laptop in your monthly line rental and you were meant to be paying the full laptop monthly bill for 24 months, not 9 or 10 and then lowering it down month after month.
I am not saying this is fair or good, but that would be o2's argument.