useless warranty

I bought a brand new apartment with a built in Defy glass electric hob. I moved in 15 February 2020 and 6 months later, the glass stove top, has a crack straight through. Nothing fell on it, there is no visible chips or anything of the sort so I called the Defy warranty claim department and received a reference number. Bare in mind this is now two weeks ago. I was told a technician will call me. Up to now NO ONE has called me so I phoned the helpline again. The guy tells me there is no comment on the jobcard so he will escalate the matter. Seriously guys it's been two weeks and it is such a mission to use this hob when the glass is cracked. It is pretty useless. Surely it cannot take this long to send out someone to come take a look at it? I mean how long will it take for a replacement unit to be fitted????