problem with changing post status to pending payment

Hi

In my website, new ads(jobs) are submitted with pending status and I want to change their status to pending_payment if their information were right, but when I try to save or update posts to pending_payment, it changes to active state automatically and I don’t know why?! I just turn off wordpress cron job and I don’t think it is related to cron job. To do my code I tested different hooks like ‘pending_to_pending_payment’,’transition_post_status’ and ‘save_post’, but it does not resolve the problem and it changes post status to active instead of pending payment. please help me.