I do not know the wallet you are using, but if not Electrum, you will have to import your seed phrase on Electrum so you will be able to freeze the coin (only Electrum on computer have coin control feature, mobile Electrum does not yet have it).
Download Electrum from
https://electrum.org and use this
guide for signature verification.
Import the seed phrase on Electrum. Open Electrum -> Click next -> standard wallet -> I already have a seed and input your seed phrase. If it is BIP39 seed phrase, click on 'option' and check BIP39 and clcik 'next' to select your derivational path.
legacy (p2pkh) for addresses that start from 1
p2sh-segwit (p2wpkh-p2sh) for addresses that start from 3
native segwit (P2WPKH) for addresses that start from bc1
After importing your seed phrase, click on view -> show coins -> click on coin tab -> then right click and click on 'freeze coin' to freeze the coins. You can freeze as many as possible inputs that you want to freeze.
the problem is how did he know my wallet in the first place?
it seems like if i send my coins to another wallet i would also just get few cents sent over to there aswell.
The blockchain is an open ledger, the person can start after noticing your transaction on blockchain and trying to connect addresses linked to your addresses together. But the coin is dust and worthless, you can just freeze the coin easily on electrum.
