Greetings,
I reviewed your requirement and i can do 100% perfectly as you want , but you need to share with me the following detail.
1) Twilio login credential or API credential
2) weglot login credential or key
3) Website demo credential for purchase , that i can find the exact location in code, where i have to write the code for SMS
4) C-panel of your development server or Prod Server. better to give me development server, taht i can freely write the code and test, once everything correct. i will move the code in prod server.
I have 9 years of experience in PHP and you can see my review 40% job based on Twilio.