i.e. pay $5 to go back 5 days.
The time travel is permanent and one-way.
Edit: this is a one time offer and your budget is however much liquid cash you have right now. Cards are accepted, though.
For non-Americans, feel free to convert $1 USD to your currency
Depends on the effects, one time theory I saw recently held that altering time was like a ripple or earthquake. The further you get away from the change the less effect you have.
So just going back in time wouldn’t stop 9/11.