Invalid application due to payment problems?

[itida]

Hello

I have been a student in England for four years and after finishing my visa in January 2016, i wanted to get an extension till July for my graduation. I got help from a solicitors and paid them to work on my case in applying for FLR(o) on my behalf; £700 for their payment fee and £200 for immigration health surcharge. I got my biometric test and did that too. Now 5 months later, my solicitor called me saying that my application has been rejected because the payment for health surcharge wasn't done. I asked if she didn't do the payment, but she is not admitting her mistake. I am going to meet her tomorrow, but i would like to know what kind of situation could rise in this case. I want to know as much possibilities as possible.

Please help

Thank you

Aditi