so someone else to me worked out the taxi for taking kids to school, worked out costs etc

all the emails she has are based on £48 a day, no mention of vat. I never saw these emails btw until now

I had to take over this as she then dropped out, took the money as she had detailed it, paid the bills etc. Realised now that she never included VAT in her projections so we are now going to be almost 2grand short this year.

Reckon there is any point arguing with the taxi company? If it was all agreed with email - no signatures or anything can we cancel at any time (this is looking likely)?
any advice/strategies, this is SUCH a shitty situation as I am the one having to tell people they will have to stump up an extra 250 or carshare their kids to school, which the taxi was avoiding in the first place because of people's work etc.

ARGH