Hi,
Normally, just deactivating the "Display a contact button on the product page" setting in the HikaShop configuration should be enough for that.
Please double check.
If that doesn't help, then either you have some caching on your website and you need to clear it, or you have some view override in your template which doesn't take into account this setting properly. In that case, you can try to temporarily rename the folder templates/YOUR_TEMPLATE/html/com_hikashop/product/ via FTP and see if it helps (and clear your cache if any before checking). If it helps then it comes from one of the view files in there. And you could repeat the operation for each file in there to identify which one is the culprit.