Actually Shoppee interface is very sux for seller...the quantity purchased shown on seller side is extremely small...and often seller can easily overlook it. Imagine if seller has few hundreds of order per day, and they can only look at each order for once like few seconds.

Back to TS issue, usually if me I'll just refund the item cost. Shipping cost is already ship with the first quantity you purchased.

Btw why the heck you need to pay shipping on shoppee...i tot got free shipping on shopee