Hi.
We don’t have any tutorial with SIM800L and ESP8266.
We have something like that for the ESP32. I think the library we use is also compatible with the ESP8266, so, with a few changes you may get it working.
Here’s the tutorials we have:

• https://randomnerdtutorials.com/esp32-sim800l-publish-data-to-cloud/
• https://randomnerdtutorials.com/esp32-sim800l-send-text-messages-sms/

I hope this helps.
Regards,
Sara