I keep getting these calls but they never say anything and I block the number just for them to call from another #

I keep getting calls from this # and they don't say anything and I blocked the# just to call me from another #

It is a company that identifies themselves as "Medical" something, and they are looking for people that are diabetic.  They have a large amount of outgoing lines, and I have received multiple calls from the same entity with varying last two digits.  I finally got ahold of someone and asked to be removed from the call list.