Hi Hector,
The additional $1.50 difference is the e911 enabled service on the phone number. Depending on how your are using the phone number you may be able to disable that service. If you are simply fowarding the number to your cell based on a time filter (which is what it looks like) - you can probably disable e911 (click the green button next to the number).
E911 is a requirement for phones that can dial PSTN.
https://www.ringroost.com/pricing.php
Thanks,
RingRoost Support Team