FICA - No help

My wife has a JOINT acoount with me wich I SIGNED for and I PAY for! When my wife went to buy clothing for my children, she went to the desk to see if everything was in order to buy and just to make sure I gave her my card too (joint) and she was told yes. Being in the store with a 2 and 3 year old for two hours standing in a line for another 30min she gets to the front desk to pay and she was told to FICA!!!!! AFTER SHE ASKED. They did not want to help her FICA or even contact me!! I know what the law states and fully agree but how can she FICA if I pay all the bills and she has nothing billed to her? I signed for her card stating she is my wife and lives with me, I take full responsibility for the card whenever she uses it! I spoke to Charlotte Baumn on 1 April 2015 at 13:06, she said she cant help me and i asked her to get a manager to call me, nothing. I work 7 days a week and dont know how to sort this out. So if I am correct i dont have to make any payments until I Fica seeing my details are not correct and cant be responsible for it seeing my signiture means nothing. I have never paid late or missed a payment but if this is your attitude against a customer the so be it.