Demanding our payments!!

So we were asked by someone from this company to do a surveys for them, give the surveys to students at my school to complete. So this took hours, cause we had to go room-to-room and the survey was quite long. So they promised to pay us after. Sometime last week they sent us contracts to sign and return them back to them with our personal information and confidential documents. They promised to pay us our money not later than the 21st of June which was Monday, it is Wednesday today and they haven't paid anything for us as research interns, we tried calling, emailing them with no response. We had been in contact with the HR manager, she doesn't even bother to explain why there's a delay. As students we took our days and did the work they asked us to do which took hours! Everyone knows how busy students are especially in this pandemic, but we sacrificed our time, just to be ignored?? Awoa!! Can we please get a response. Thank you