It might be for a few reasons. Verizon might not have your CO marked to offer the speed yet. You might be for example in a BPON area which does not get provisioned for 150Mbps/70Mbs due to capacity concerns. GPON areas get 150Mbps since GPON has far more capacity. It might also be an error in the Address database where your home is able to get 150Mbps but is not seen as capable in the system (perhaps due to the previously mentioned reason). If this is the case it will take someone with the ability to correct the database to get service ordered for you, or at least get the ball rolling so that it may be ordered.
Do you know what ONT you have? If not, try opening the customer access portion of the ONT up. It should say who the Manufacturer is and what model ONT. If it's GPON, I can't see why you cannot have 150Mbps. If it's BPON, we'll need to see if your area is GPON-capable. As long as it's GPON-capable, I cannot see why you cannot get 150Mbps as Verizon will move you to GPON when they come out to do the install.
How come on Fios website they show that 150/35 Mbps is available in my area but looking at the upgrade center and calling customer care the do not offer this in my area?
Wait forever, and perhaps 10GLTE wil be faster.