I have no intention of paying them back
So if you were to pay them back anyway, would that make you more or less honest for changing your intentions?
Not more or less honest, just honest.
Intention: Plan or Aim of doing something. So, If I paid them back, I'd still adhere to the original statement. You just shouldn't 'expect' them back.
Now, If I said: Shall Not pay them back. I wouldn't be true to my word if I did pay them back.
And in that case, if I paid them back you shouldn't trust me. But at that stage, the argument is moot, is it not?