Twilio has a pay-as-you-go model, but offers a free trial credit to start with.
Telnyx offers free inbound SMS texts, but charges $0.0045
Per Outbound Message.
Plivo is another SMS service that has pay as you go pricing, but offers free trial credit.
Messagebird, like Telynx, offers free inbound SMS texts, but charges for outbound SMS messages.
ClickSend inbound SMS messages are free, but outbound SMS messages depend on volume.
|2k or more||$0.0088|
|10k or more||$0.0073|
|100k or more||$0.0067|
|Over 200k||Custom Pricing|
Wavecell pricing varies by country, but you can get started with a free trial.