What is the meaning of prefixes like DZ, DM, IZ, etc.?

When a recipient receives a message from any provider or bank etc., a sender ID along with a prefix is displayed in the inbox. For example- VM-ICICIB, BW-Google, DM-Amazon, VM-Redbus, etc.

The prefixes VM, BW, etc. are displayed because SMS is sent in huge numbers via bulk SMS. SMS providers follow rules framed by the Telecom Regulatory Authority of India (TRAI) and according to TRAI rules