It turns out, it was VISA's fault...

Visa admitted that recent excessive charges to Coinbase customers' debit and credit cards were the fault of Visa, not Coinbase. Customers had been charged duplicate fees for previous transactions, in some cases, for extremely high amounts, causing overdrafts and insufficient fund problems on bank accounts tied to Coinbase accounts.

In this article, Visa assures Coinbase customers that charges should be refunded and will appear on customer accounts in the next few days, if not already.

This could potentially be damaging to the reputation and client trust of Coinbase, despite Visa's clear admission of fault. It is likely some Coinbase customers will look into alternative services after being charged excessively for their cryptocurrency transactions. Of course, as long as customers continue to use centralised services such as banks and Visa, they will remain at the mercy of such agencies.

Hopefully, all of these mistaken transactions get cleared up over the next few days. Visa recommends clients should contact their card-issuing banks regarding any incorrect charges remaining after this reversal period.

source:

https://blog.coinbase.com

image source:

https://themerkle.com/visa-and-mastercard-now-charge-an-additional-fee-for-buying-cryptocurrency/