I don't think anyone has an offline transaction service yet.
so far we can only transact if we are connected to the internet, but if the internet is off we can't
do anything.
This project is very useful if the internet is off, we can still make transactions. I think someone must have thought about it
it may still be under development. At the moment I know of only crypto wallets that can store coins offline in a dedicated hardware wallet.
Hopefully in the future it can be realized transacting offline.
The world of crypto transactions today were very dependable on the internet and if in case it happen that there will be a one day without internet then it will be a nightmare for every one crypto trader and investors. So far, I haven't heard any transactions made thru offline and it will be breakthrough to crypto platform if one day transactions offline will be available before the any internet disruption occur. However, if it happen then it is not only the crypto platform the very affected because almost all transactions of the worlds system today mainly depend through internet.