Talk to your mobile service provider. only they can activate your phone.
That isn't true.
You can reboost a boost phone online by launching it from the phone in question, and then reset the handset by going into the bios on boot.
You will pay a ten dollar reactivation fee and require a credit card.
If you don't reset the device, it won't re-establish a link as it will have settings from the previous activation and number.