Hello. Can't answer that much without more info. I had similar situations on a previous plan in the UK (you may be in the UK). I found I could ring and ask for extra data for that month (£5 per 500mb I think). This was added to next months bill, and I could revert to my 2gb allowance by opting out the following month.
Speaking to the carrier/network would be best. Even if you don't have the money right now. It's bound to be cheaper than going over your allowance by asking about temporary add - ons / bolt - ons of data.
Set your Data Usage limit on the device.