I've sent several proposals which all had 6 different people asking me to either message them on Skype or Telegram. There were two pairs of postings(4 total) that had different titles and descriptions but when I messaged them, they would send identical attachments asking to message them outside of UpWork. I've only held conversations with 2 of 6 just to see where it went and each time I was offered a job but they would ask for an address and say that the company would send a check for supplies.
I'm really sorry to learn about this unpleasant experience. A real client will never ask you to give them money to start working, cash a check for them, work for free, or provide your personal information. I would also like to let you know that sharing contact information before a contract has started is against Upwork's Terms of Service and that all communications prior to the contract starting must take place on Upwork. We also encourage you to let us know if a TOS violation has happened by using the Flag as Inappropriate option throughout the platform. You can learn more about user reporting here.