I worked for four months with Avance Consulting, which was the worst experience I had in my whole working life.
It is noteworthy that they do not really have any offices in Poland, the address in Warsaw is only a mailbox address and all their Employees are Indian-based, they are charming at first but are hard to reach and will generally not answer LinkedIn messages or Emails if there are any problems.
I worked along with 3 other contractors which were also employed by Avance Consulting and none of them was paid in time, now I left 3 months ago and the client paid long ago but I still received no money from Avance Consulting.
They tried to convince me to keep on working for them regardless of the fact that I have not been paid, but they keep telling me that they have "communication problems with the Client" and I will be paid later, now I have engaged a law firm to enforce them to pay the open Invoices, after doing some research I have learned they have a record in not paying invoices before legal steps have been taken.
Avoid them like a Plague or you will regret it.