Hey /sci/!

Today I come to you with a genetic riddle:

I'm B+ blood type, the same as my father. I do not know my paternal grandparents blood type, but I know that my maternal grandparents were A+ and A- my mother is A- like my grandmother.

Statistically shouldn't my blood type be AB or A?

To my understanding even if both my paternal grandparents were type B (very unlikely as it is a very rare blood type in both of my parents countries) I shouldn't inherit the B blood type as there is a strong pull from the A side so the closest I should be to B is having AB blood.

The wiki page on blood types says that even in case of combination of A and A alleles with B and B alleles the offspring would either be A or AB.

So, was my granny a cheating whore or were my dad´s genes just too alpha (or beta in this case lol).