Phippy,
Those codes are the golden grail of Telecom billing. Each time I work with a different telecom vendor I need to confirm what they mean by the codes, many such as 1mb stay the same. The problem you will encounter with many vendors is that the code is placed by a human for billing purposes, and as such it doesn’t really mean you have that exact service or option. A few books on billing have listed the general ones out. If it would help you I can pass on a few titles. But from my experience – you need to determine what a particular vendor uses and what they use them for.
Good luck.
Jason
PS – by the way it was nice to see a general Telecom question pop up on here.