Can I change GC seals for another's?

I want to change GC and I have 80K seals currently is there any way/trick to easily convert them to another company's seals?

I don't think so but it would be nice if possible.

You cannot, unfortunately. You don't lose them, however, so if you ever switch back to the other GC you'll be able to spend them on that GC's items again. What I did when I switched was buy a bunch of items I knew I would want until I had no more to spend. E.g. ventures, minions, furniture, etc.

Buy gc greens. turn then in after you switch gcs and rank up a bit. You will lose some in the conversion but if you never plan going back it is better than nothing.