Hi,
I have implemented Twillio API in my previous project, in which I'm sending SMS to the user with links, in another project I'm sending SMS to the donor for donation, the donor will reply as Campaign Amount and a donation will be made :)
I have worked on both sides, sending and receiving. Your requirement is also simple, you need a textbox, so a user will add a mobile number and SMS will be sent. I will start right now :)
Ping me back, so we can start ASAP.
Thanks and Regards,
Nabeel Abid