My partner has just had a letter with this 'we're sorry you left' offer, its better than online because in order to get the voucher online you have to add another option and with this you don't.
I have been with the AA in the past and although the letter wasn't for me i thought id give it a go and it worked.
Phone number 0800 1976709
remember - the voucher comes in 4 weeks by email and may go to spam folder, so check. Also remember to cancel next year, they say they send a letter but sometimes the AA conveniently forget.
I don't really worry about my car breaking down, only getting a flat tyre in the middle of nowhere so this is worth it!