Companies or ICOs are hiring people who is willing to wear their signature in their every posts to promote them, that is how a signature campaign works. There are so many investors here in this forum so they want them to notice their advertisment through posting. You can't do other campaigns other than the one you have joined. The salary depends on the rank respectively. Campaign managers are strict and they made rules for this such like constructive posting is needed, otherwise, you will not get paid if your posts have no content.