So many opportunities missed to avoid this! Look at one ID and ensure it is what you expect it to be. Run the script in a dryrun mode. Run the script for 1 customer. Probably more!
[0]: https://www.twilio.com/docs/glossary/what-is-a-sid#common-si...
It's puzzling to me that we, as software developers, spend so much efforts trying to automate such one off deletion tasks, and the automation would inevitably go wrong and result in data loss.