Help regarding migration fee

I need clarification on the migration fee. I have spoken a customer care rep and the answer I get is "It's mandatory". I have done my own research regarding this fee and come to find that it only specifies one reason for implicating the fee. To my understanding, the fee is charged when a customer changes from a classic plan to a value plan. I haven't seen any other documentation, discussion, or "faq" stating otherwise. If there are other reasons that apply this ridiculous fee, please let me know. I have a situation in which this fee must be charged and want full understanding of it.  I have tried to get someone from T-Force to help, but seem to be unable to get any kind of response so at this point any reply will do. Thank you