If they claim it can rewrite the UID, then most likely the white cloner locked the chip.
In which case @Pilgrimsmaster’s first post here might be your solution, and you would definitely need a Proxmark.
Now to the real question… why on earth would they sell a white cloner, especially if they also sell chips the cloner can brick? 
Hate to be the bearer of bad news then…
Here’s the datasheet from EM Microelectronic who manufacture the EM4102. Notice the big writing that says Read Only Contactless Identification Device
Option 1 - EM Microelectronic are incorrect (this isn’t the case)
Option 2 - They lied to you when they told you it was an EM4102 implant, and the CEO is right now in saying they are rewritable
Option 3 - The CEO is either lying or misinformed in talking to you now and they aren’t rewritable
Option 2 and 3 don’t make me feel so good about the company at all…
Yeah woohoo bioteq … said noone ever.
Honestly only ever had one dealing with them and it was awful never emailed them again.
God the typos in product names don’t inspire confidence (I know it happens but cmon man, even in the name of the document!)
Actually, the mere fact someone has to go to the length of even considering those is already awful!
And well spotted. when I read that mail I just assumed there was something about that chip which I was unaware of.
Not that they could be so grossly wrong about their own product (either on name or functionality)
