Hello.
I have checked your platform forums.
I am a senior web developer and also have plenty of experience in POS.
As I have made an Android POS app, I am good at about how a POS System works.
I have plenty of experience in Node JS and PHP also with MySQL database.
I think I can help your project though I am not so good at FreeSWITCH.
As I have over 12 years of experience as a developer, I can learn everything quick and implement it for your app.
Hope to discuss with you about your app.
Best regards.