IDFC Bank — Spammer Bank

Despite repeated complaints with screenshots as proof of their spamming submitted to IDFC Bank to their Head.[protected]@idfcfirstbank.com
I keep getting spam mails from them. they are very smart and are able to bypass the filters by changing the headers/ sender ID as IDFC, IDFC-First, IDFCBank, IDFC_Bank etc. They spam regularly through their marketing leader PoonawallaFincorp alias [protected]@connectinboxx.com.
Can some legal luminary advise how to fix these spammers.