You bitcoin client (core in that case) should sort this out after a few new blocks. (So just wait for more conformation as one of the tx will be dropped if the other will stay).
If it won't sort out itself you can perhaps also try to -rescan your wallet.
Hope that helps
Shouldn't the Bitcoin Core's latest version which was patched for this sort of attack stop this? Or maybe OP is using the older version Bitcoin Core.
Which version are you using OP?
And if you notice the two transactions they have different fees. It's not possible for the attacker to change the fees, the first one has a very low fees. I don't think this was the malleability attack. But can't say what happened.
To my understanding:
You initiated this transaction first: https://blockchain.info/tx/64447ecaad274a2d4edb7e9716f4dbf1cc8a871bd29ac815497968dde91f6234
The next day, you initiated this transaction: https://blockchain.info/tx/a15f81a67cb3b990ab89c36a15348db66ab8f39c6007e4c9ed6b8631eb936fe7
And this transaction: https://blockchain.info/tx/c471d60bece79ffad8cb5230d3dd80da1b351b3a3a21c054b490b59193880d7a.
The first two transaction will not confirm because the third transaction has already confirmed. They are definitely not malleability attack since all of them have different fees.