Contract law is not my strength!
But I agree with others' comments. In these times where public health has come to the fore, they were within their rights to pay you electronically and, as they have changed the terms of your original contract and as a result your bank expenses have gone up, you'd be within your rights to therefore increase your prices to cover that extra cost.
But, cash in hand is suggestive of tax evasion (I am not saying that you are evading tax by payment in cash, just that it can look suspicious) and therefore it may also be that what is now clearly not such a temporary job, must be paid through what looks like more legitimate means and that would not raise any auditor's eyebrows.
Who knows?
Your choice is, as I see it, to see if you can negotiate increased costs, walk away, or continue with the arrangement as it currently is.