You're correct that an early termination fee is generally unenforceable. You can sue in small claims
court and try to recover against the vendor. However, due to the nature of this type of action, even if you win, collecting your judgment could be extremely difficult. Because of this, you may want to consider filing a complaint with the State Attorney General.
If you decide to sue in small claims, then please review the CELLPHONE FEE TERMINATION CASES, 193 Cal.App.4th 298
(2011). The case contains a detailed discussion of "liquidated damages" beginning at section entitled, "B. Section 1671."
The section describes a two-part test required to validate the early termination provisions of the contract
. That's what the vendor must prove in court -- and it's what you must disprove. But, the vendor is required to go first, under the presumption of invalidity accorded to consumer liquidated damages provisions.
The issue of the use of your EFT withdrawal being revoked at contract termination is a much more difficult question. I have researched my legal data service for case law on the subject and I am not finding anything relevant to California. There are some "unreported" cases. But, such cases may not be cited in court -- they are merely for research purposes to get a sense of what a court may rule sometime in the future. As such, they are of little value. Moreover, I cannot link to the cases, because they are not published outside of my database.
You can certainly argue that the termination of your contract also terminates the vendors authority to draft your account via an EFT. If I were the judge in a small claims court action, I would have to think hard about whether or not that theory is viable. I can see arguments for and against: (for) termination may be a breach, but it's a termination nonetheless; (against) termination is not a breach, as long as the cancellation fee is paid, so vendor can draft the consumer's account to completely extinguish the contract).
Frankly, I think that the liquidated damages argument is stronger.
Please let me know if I can be of further assistance.