I think the original contract is enforceable at the time it was originally agreed to. Coming up with additional terms, even if they were on the same day, wouldn't not change the original contract. Imagine signing up for a credit card offer and then sending a certified letter to the bank informing them that you will only pay a lower interest rate that you designate.
I think the stronger argument is the "incorporated by reference" argument, given the fact that those could be changed at a later time. The terms of a contract need to be clear, and any ambiguity would likely be settled in favor of the party to be charged.
I have always been suspicious of the "Click to Agree" box at then end of a long contract that no one, including the company offering it, has ever read. The problem is that there are so many (generally unlikely) contingencies that have to be accounted for. What other choice is there when there may be substantial liability in question?
It’s about required notices. Basically the contract has opt-out provisions that they hope you either won’t notice or will forget to opt-out of.
The idea is simple, you just reverse this dynamic by immediately and pre-emptively opting out of every optional element of the contract that could cause you to incur additional financial obligation.
If the contract says you must give a non renewal notice by X date or you agree to a renewal then the letter is written notice. The trick is making it the same day you sign the deal and making it all inclusive.
It doesn’t change the existing contract it abides by it.