No, you're perfectly allowed to not upload payment info. If no idle fees are ever assessed, you'll never run into a problem. And if they are, you can pay for them after the fact. It's just that by choosing to incur a balance instead of automatically paying, you may be temporarily prevented from using the superchargers until your balance is cleared. But that's a choice you're taking at your own risk.
EDIT: I can't edit my first comment, but here's the particulars that I couldn't initially recall from
Tesla's page on Idle fees about running a negative balance:
If a payment method is not set up, you will receive alerts on your touchscreen and via email. If outstanding charges accumulate past a set amount, your Supercharger access will be restricted until the outstanding balance is paid. Supercharging can be immediately re-enabled by paying the balance on your car’s touchscreen or in your account.
I purchased the car with an included service that was unlimited. Changing the rules now is breach of contract.
Tesla hasn't promised to positively provide that service to you**, they've only promised not to bill you for your use of it. And they won't, either because you successfully charged and, because you have free supercharging, there was no fee for the electricity or because you couldn't start a charging session and there was therefore no electricity delivered (and by extension no bill).
** If you're having trouble understanding this point, consider these questions: 1. There are plenty of Tesla owners in Hawaii, many of whom purchased cars with the same free unlimited supercharging service included. But Tesla has so far totally restricted those owners' ability to supercharge by not installing any supercharger stations anywhere that is reachable by those cars (i.e. there aren't any in Hawaii). Can Tesla be legally compelled to install superchargers on the islands in order to ensure that those drivers actually have the opportunity to use this "unlimited" service? 2. You're driving to an isolated supercharger to charge and will arrive with a very low battery SOC, too low to reach any other supercharger location. On getting there, you find that all superchargers are unpowered and off-line. Can you sue Tesla for breach of contract because their state of non-operation has limited/prevented your ability to use this "unlimited" service?