Just wondering if anyone can help out with some advise

I bought my house 6 months ago and paid solicitor final bill etc then.

Now i get a letter 6 months later saying land registry fee's have gone up and i owe them more money

My question is should that not have completed the land registry stuff 6 months ago when i completed the house purchase? Is it their problem that they havent bothered and now the fee's have gone up?