Hi Barbara,
If it's truely a GTC (not using the Auctiva Auto-Relist feature with PROFILE), you need to END/CLOSE the listing at eBay. If you are nearing the end of the current 30 day listing, just make sure you end it at a convenient time before it recycles to another 30 days.
FYI, to Stop Auto-Relist and end, you first stop the Auto-Relist on the Active Listings page at Auctiva, then end the listing at eBay.
Danno