Woo Commerce over writing css?

Woo commerce looks lovely but the support is terrible and the replies from support sarcastic and snarky, never again.

I've made a nice looking site with the Atahualpa theme and a Woocommerce plugin.
The trouble is that something updates automatically and the font colour of the price changes to white, which means it looks like it vanishes.

This is one of the pages it is happening on http://www.mamablessings.co.uk/produ...gift-vouchers/
The black text with the £ amount on just above 'add to cart' turns to white text and vanishes.

The coding is beyond me so I outsourced it but it's still being over written by something ever now and then. All that Woo said is that the coders didn't do it properly and sent me to a link that says to use a child theme, which I don't think I can do with Atahualpa can I?

The coders I outsourced to changed the css on the WooCommerce, can I add it to the inserts on the theme instead? Would that make it stick? I'm not actually sure what they changed anyway.