(Some of these have free trials needs to be cleaned of ones that provide free trials with ability to receive sms. Twilio does work but it is not always good for google.) Sign up using temp email to make a trial account on the ones that offer free trials. Also a last resort option to using your own phone number if you choose to purchase a temp number.
Available SMS Gateways
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1. Twilio
2. Clickatel
3. Text Local
4. Asterisk
5. MSG91
6. Plivo
7. SMS Global
8. Bulk SMS
9. Nexmo
10. Route SMS
11. SMSKaufen
12. Kapow
13. Zang
14. InfoBip