5 hours ago I withdrew bitcoin from online service with 20k satoshi fee and transaction was processed instantly.
Are you sure your fee was good enough?
Same here, and waiting for less than an hour I did not consider it as a delay. Sometimes less than 30 mins and its already fine. Usually fees range from 20,000 sats to 50,000 sats in some exchanges.
Just wait , as long as your transaction is on the blockchain already I think it will not lost.
I cannot understand why you claim that fees range from exchange to exchange. If I'm not mistaken I believe is not matter what exchange anyone uses but what is the transaction size and how many are the unconfirmed transactions (network load), except if is a service which offered from some exchanges where customers pay a standard fee regardless the transaction size. Unfortunately, these days the fees are very high from 60-70 s/byte to 140-160s/byte if someone wants a next block confirmation.
oh it does matter which exchange.
i guess he meant user transfer fees range from 20k to 50k, well from 10k on poloniex.
polo aggregates user payments and applies adaptive fee,
which garantees not superlow yet comfortable transfer delay,
some exchanges (many actually) don't have that mech, and things look ugly there these days.
an example of typical poloniex transfer:
https://blockchain.info/tx/7d6eb1732f0abbedb9846f47d15dfef573555385b957ea3b1a5e3b9ebfe4cbf3