No unlimited plans from Twilio, unfortunately. https://www.twilio.com/sms/pricing
Maybe another SMS service offers that? If so, I'd certainly consider SMS again.
Maybe another SMS service offers that? If so, I'd certainly consider SMS again.
One option would be to re-enable the SMS option for people who deposit money to cover the SMS fees. Mark them up 100% (so 2c per SMS or something) and you'll have a built-in profit margin.