Even if you did get seeds from large white dahlias there's hardly any chance that you'd get a fully double large white dahlia from those seeds. Most times the seedlings are absolutely nothing like the parent-- not even similar!

Would i atleast get a white dahlia from the seeds?
If yes then i still want it! I hybridize cannas, so im guessing there is a chance i might get something beautiful from the dahlia seeds anyhow! I just want a white one lol.
Please someone... help me!

The odds aren't great that you would get a white one even if you could find someone willing to part with seeds from large dahlias. Dahlias have one of the most complex gene structures in the plant kingdom so the odds of getting anything like the parent are similar to the odds of a human child being just like it's parent! Large dahlias are the hardest to hybridize & set fewer seeds than any other sizes, consequently, most people who do get seed from AA or A sized dahlias use them all themselves- I know we do!

Well, I hope some generous person would help me out a bit, and trade with me.
A few seeds arent much to spare.
I hope someone has some seeds they would like to trade with me :)