Switch axis so phone is flat with accelerometer

I am working on a game that uses the accelerometer to move a ball with the mobile phone as a controller. I got it to work with this script but I'd like the change one thing-- I'd like the phone to be layed down with the screen up as as neutral (no force being applied) verses how it works right now with the phone is up in landscape view I'd like it to work like this.

this is the part of the script that takes the accelerometer and turns it into steering but I can't for the life of me figure out how to flip the axis so that +Z is up.

accel.x = accelerometer.ACCELERATION_X; accel.y = accelerometer.ACCELERATION_Y; accel.z = accelerometer.ACCELERATION_Z;

     //accelerometers due to gravity can really only sense 2 axis (can't filter out gravity)
     //here we convert those 2 axis into horizontal and vertical and normalize
     horizontal = EasyWiFiUtilities.relativeAngleInAxis(Vector3.up, -accel, Vector3.forward) / normalizeDegrees; //forward to right
     vertical = EasyWiFiUtilities.relativeAngleInAxis(Vector3.up, -accel, Vector3.right) / normalizeDegrees;

     horizontal *= -sensitivity;
     vertical *= -sensitivity;

     actionVectorPosition.x = horizontal;
     actionVectorPosition.y = 0f;
     actionVectorPosition.z = vertical;

     myRigidbody.AddForce(actionVectorPosition);

Can you help me figure out where in your script I can make the adjustment?