Falsely accused of data theft by company

Hi, I was working in a call center in Kolkata from end February to end march, the salary was as low as 16k per month but due to lack of better options I did, but after completing a month I got infected with chicken pox & informed my employer about it & also send a copy of prescription of my diagnosis, while recovering I got an offer to start working for one of my previous employers for a higher package of 23k per month hence I decided to join that company, the only mistake that I did was I didnt inform my current company about joining the new company as I wanted to work for 3/4 days in the new company before resigning from my old company, to my surprise I received a whatsapp msg stating that I have lord about having chicken pox & even I sent them a false medical dox & moreover I have stolen data from them & duped one of their foreign client of 30,000 Pounds & I need to compensate that, while I have done nothing of that sort & have send then photos of pox marks, pls guide.