I see that as one of the challenges that you face on your job. It could be better if you are contacted through your mobile phones number. After all no one is expected to sleep on social media platform all day..It's one of experience we freelancers have to live through all the time. There are times when you can't be online and that's when you will be contacted to work on an order. If the client doesn't give few hours for you to come online, they will give out the job to another freelancer who's available online.