Network monitor without backdating?

Are there any network monitor tools out there that don't practice backdating on support renewals?

We are currently a few years behind on support and would like to renew with our current vendor, however, they want to backdate our support contract to the day our support ended. This means we would be essentially be paying the full cost of the product we originally paid a perpetual license for.

I understand paying for the software update portion, however, it seems rather unfair to pay for the time when we had no access to support. I have spoken to two other companies and it seems they also follow in this vile practice.

Essentially they bundle software updates in with support in order to extort software update pricing to the tune of 25% per year. It seems that while this practice may be widespread, it should be illegal.

TIA