You can cancel a Solana listing at any time, and changing the price works the same way.
Open the item from your profile and click Cancel listing.
Approve the transaction in your wallet. Canceling is an onchain action, so it needs a network fee in SOL, and you sign and pay for it yourself.
The item returns to your wallet in the same transaction, and the account deposit goes back to whoever paid it.
To change your price, cancel the listing and create a new one at the price you want.
Listings are canceled one at a time on Solana, so there is no way to cancel several at once, and there is no free cancelation. Listings you created on another Solana marketplace need to be canceled where you created them.