Short Term Rental Squatters. Won't Pay, Won't Leave!

[William Coet]

I signed a 2-month rental agreement with some engineer contractors from out of U.S..  They are refusing to pay and will not leave the property.  The apartment is in very nice condition and they are entirely unjustified in not paying and refusing to leave.  They want to live for free for the second half of their stay.   I have another short term rental possibility with another group if they leave, and I do not want to lose the income.

Any suggestions on how I can get them to leave?

Thanks!