I think that the petition will be useless without action. What do they care if you sign a petition and still pay them for their crappy service? They can easily just ignore you. This would still be true even if all of their customers signed the petition, and still paid for the service. If you want to have an actual impact, sign the petition, and discontinue service with them, sending them a letter telling them why. Otherwise, your money will spend the same, regardless of how dissatisfied you are with what you are paying for, and it won't make any difference to them.
The point of their service, from their point of view, is to make money, and the only way you will get their attention is if you affect their ability to make money. Everything else is irrelevant.