how to change postfix mail server port

i want to change my postfix mail server port from 25 to other because my vps provider blocked port 25
i add in  /etc/postfix/master.cf   this config for

26       inet  n       -       n       -       -       smtpd
 but this can't work for me i restart my mail server but still work in port 25


May 12 09:19:40 cp postfix/smtp[13624]: connect to alt2.gmail-smtp-in.l.google.com[108.177.8.27]:25: Connection timed out
May 12 09:19:40 cp postfix/smtp[13625]: connect to alt2.gmail-smtp-in.l.google.com[108.177.8.27]:25: Connection timed out

please help 

you can't change it and can't send email out of server until and unless port 25 is closed.