Application of GST

Hi
GST is applicable state wise. here is my query:
Am in Logistics & Supply Chain Industry:
Our customer is in Tada ( in Andhra State). All their shipments are executed thru Krishnapatnam port ( Andhra State).
Billing done by Chennai office .

Should I follow which state gst provisional I'd to customer. that is Tamilnadu State provisional id or Andhra state id.

kindly clarify in brief.

Thanking You !!

Kumar. D. K.