I have recently had the same thing happen with Aaen Peach.
https://www.consumeractiongroup.co.uk/forum/showthread.php?471450-Aaen-Peach-lawyers-fees-received-a-bill-for-title-transfer-and-remortgage-for-£1-400
I wrote a lengthy complaint & asked for evidence of the additional works & after review I was advised that I had been billed for work incorrectly.
Initially when I queried the bill I was told that it was correct, I had to put my complaint in writing & ask for the breakdown before my file was reviewed by a senior partner.