Somone is giving out wrong information. To add another line, you cannot be on the spending cap program ($200 limit on the account)
If this is not the case for you, I see no reason why you cannot add another line. What you could do, if you wish, is to call Koodo again and ask them what your credit class is. Here is how it will work...
Credit class X = no additional line
Credit class L = no additional line
Credit class D = yes
Credit class B = definately yes