There's no way to get rid of link transfers if it was not uploaded from a WeTransfer account. Once you complete an upload, you'll have to wait until the transfer expires. That means the regular 7 days apply. Please check that you are sharing the download link with the right people before doing so.
If you've got a WeTransfer account, make sure you log in before starting an upload. That way, you can always look up a transfer in your 'Sent' log. Here's how to get rid of transfers from your 'Sent' panel:
If you'd like to be able to delete your own transfers in the future, please consider signing up to our free accounts. You can learn more about them right here.