Weddingbee boards

So, I'm a natural 38FF (yes, your eyes do not deceive).  I bought a strapless Goddess bra (#689) about 3 months ago, before I bought my dress. Well, I bought my dress and I have had it for about 2 months.  I just finally took it to be altered and it's clear that the strapless bra I bought shows and rides higher than the top of the neckline/bustline of the dress. 

So, I go to take the bra back to exchange it for one that lays a bit lower on my booby and the bra salesman (specialty store) tells me there is no way, no how I will find a 38FF bra that lays any lower than the one I already had.  I am devastated.  What can I do?  I can't get another dress! 

My dress is a Paloma Blanca 3967: http://www.palomablanca.com/3967

The Goddsss 689 shows at the peaks of the breasts and under the arms! 

Any ideas?

I am nowhere near a 38FF, but I am having a similar problem with my dress (finding a bra that won't show).  Given the lack of options, I suspect that altering the bra is your best bet.  It could get difficult, especially if boning is involved, so you should take it to a professional.

Thanks for the advice everyone.  I went ahead and bought two bras for shipment overnight through HerRoom.com.  I'll see, once it arrives, if it can be seen with the dress on.  If that doesn't work, my last resort is to do as suggested and bring in the original bra and have her alter the bra.  I didn't even think of that as an option originally.  I guess if she can alter the dress, she can alter a bra!