Parasol put up their margin 55% without any notice, any suggestions on a different umbrella company to switch over to?

One for those experienced with umbrella companies, and perhaps contractual notice periods?

Here’s the story:

I was just checking my payslip and noticed that all of a sudden the margin has shot up!

I’m not accepting this, it is insane! So I need to find another Umbrella asap.

The contract says I need to give them 4 weeks notice.

It also says that they need to give me 4 weeks notice for any significant change, and 2 weeks notice for any minor change. I would argue that the margin is a massively significant change!

Instead of giving 4 weeks notice, they buried the price increase in an email about tax year end bits sent out 31 March - and implemented the price increase a week later.

So my instinct says to simply say no, and to switch over to another company ASAP. Anyone else had to deal with the same issue?