Unfortunately different brands are sized differently. This style comes in a 36A if that would be better than extensions.
Grandma from Utah
There are two details of the bra that might be giving the idea that the bra runs small, but it runs true to size. The bump pad gives a very big lift so you may feel as if you are spilling out. This bra is also a DEEP plunge bra. You are right about not having to use the straps. This style is first and foremost a strapless. The straps are for "added security".
Lauren from Long Beach