# SMS Guides | VeloBotix

> Practical guides: send OTP SMS in Sri Lanka, bulk campaigns, Sender ID and GSM-7 vs Unicode.

Source: https://www.velobotix.app/resources/guides

# Guides

-   [How to send OTP SMS in Sri Lanka](https://www.velobotix.app/resources/guides/send-otp-sms-sri-lanka)
    
    Generate, send, expire, verify — with VeloBotix API.
    
-   [How to send bulk SMS in Sri Lanka](https://www.velobotix.app/resources/guides/send-bulk-sms-sri-lanka)
    
    Step-by-step bulk SMS in Sri Lanka: clean list, Sender ID, GSM vs Unicode, schedule, and read delivery reports on VeloBotix.
    
-   [Custom Sender ID in Sri Lanka](https://www.velobotix.app/resources/guides/custom-sender-id-sri-lanka)
    
    Register a brand Sender ID on VeloBotix so OTP and campaigns show your company name instead of a random number.
    
-   [GSM-7 vs Unicode SMS](https://www.velobotix.app/resources/guides/gsm7-vs-unicode-sms)
    
    English SMS uses GSM-7 (more characters per credit). Sinhala, Tamil and emoji use Unicode (fewer characters). Plan copy accordingly.