Accounting Entry for GST bill which is paid by Credits/Balance

Accounting Entry for GST bill which is paid by Credits/Balance

There is shipping platform named Shiprocket. I have bought a plan which costs me 19116/- and gives me credits to ship products and after successful delivery, charges gets deducts automatically from that credit.
I got a GST invoice for the purchase of credit which I entered in zoho books without any issue.
But I am also getting monthly invoices for the deliveries which gets deduct from the credits.
What should be the entry when i am not paying anything.