B has the sound of P and is 9.
S as in Sauce, and Z are sounded as C (soft) so that either C, S or Z can be used for 0.
The Complete Code
Letters and Sounds Seldom Used
The following are sometimes used and from their SOUND have digit value and should be noted for completeness:
Q sounds similar to K and is 7.
X is pronounced EKS, has the KS sound and is 70.
Hard Ch as in ACHE has the K sound and is 7.
Gh and Ph as in Cough and Phone have the F sound and are 8.