The simplest way is to contact the primary card holder and ask them to remove you as an authorized user. If for whatever reason you cannot, you can dispute with the credit bureaus. Dsipute and select "belongs to primary account holder". That is what it is called on EX.
TU has similar options. EQ you will have to select "other" and explain you were not the primary account holder. Good luck.
I just returned from financial hell. Don't go, the brochure is a lie.