sms contacts problem

hi, I recieve text messgaes from my bank and credit card company and would like to assign pictures to them. I think the only way to do this is to add them to contacts and assign the picture there. The problem is these text messages do not seem to be from a number and when I add one of them to my contacts, my sms app thinks the other message is from the same contact. I am currently using chomp sms, but I have tried all others and the problem is the same. Can anyone help please.