HDFC Bank — not received the fastag sticker

Address:

RAJ KUMAR GOEL INSTITUTE OF TECHNOLOGY (PHARMACY), 5TH KM STONE DELHI-MEERUT ROAD GHAZIABAD, Ghaziabad, Uttar Pradesh, 201003

I have applied for FASTag through HDFC net banking on 06/12/2019 with a payment of Rs. 500. I have been issued customer ID and wallet ID through SMS/email during first week of Dec 2019. Based on the email, I have accessed my FASTag information online by register HDFC FASTAg. Rs. 300 also credited into my FASTag account. But unfortunately as of now I have not received the tag. I have been making calls to HDFC FASTag Customer call center number i.e.[protected] everyday but allways number getting busy.
what to do now. please refund if it could be.
Regards