How to solve Facebook mobile number verification if I changed my mobile number?

Well…I have changed my mobile number recently but I forgot to change it in my Facebook. And now, the Facebook ask me for mobile number verification. I can’t receive text from my old number. I have try to contact Facebook but I just found that they do not have customer service! What should I do to contact Facebook for help? I just can’t lose my account.

P.S. I am not a American. So, the one way for me to contact FB is to email them…