Meh, the only working free/paid accelerator online that I know is viaBTC, others are fakes or rebroadcaster marketed as accelerator.
Paid accelerator is a joke even if it's working, use RBF/CPFP with high fees is more reliable & less privacy risks.
And you can also use the RBF method and just increase the fees for your unconfirmed transactions anytime.
Or CPFP with high fees if you also plan to make another transaction