2017 BMW 330E Wheels Problems

I'M LEASING BMW 330E. IN NOVEMBER 2017 I BROUGHT IT WITH 5,800 MILES FOR MAINTENANCE TO THE WEATHERFORD BMW; WAS ADVISED TREAD OF REAR SET OF TIRES IS DANGEROUSLY SHALLOW, UNDER 5 MM. THEY ALSO TOLD ME THAT FRONT SET IS STILL OK WITH 6 MM, BUT SOON NEEND TO BE ALSO REPLACED. I CONTACTED THE BMW NA, OFFERED A 50% DISCOUNT ON A SET OF NEW TIRES. THIS OCTOBER 2018 AT 2ND SERVICE SERVICE I WAS ADVISED THAT THE THREAD NOW ON THE REAR SET IS UNDER 3 MM AND PRESENTS A SAFETY HAZARD TO CONTINUE TO OPERATE. THE FRONT SET OF TIRES HAS ONLY 4 MM REMAINING THREAD. THE VEHICLE HAS ONLY 11,250 MILES ON THE ODOMETER. WHEN I CALLED THE BMA NA ABOUT THEIR LAST YEAR OFFER, I WAS TOLD THAT THEY HAVE "TAKEN THE OFFER OFF THE TABLE". BMW BILL FOR THE NEW 2 TIRE SET...