You can cancel/eject a Bitcoin transaction but you would have to pay a fee. The fee for cancellation or ejection is more than the transaction fee. I have cancelled transaction on the same day using Electrum wallet. It does give you the option if the transaction takes more time. For me it took like 12 hour or might be more.
If you are using Mycelium wallet then I am not sure but, I am certain that my it does provide you the option to cancel a Bitcoin transaction.
Yes there is a feature like that on electrum but what it means is that you’re actually double spending your transaction to your own address by paying higher fee. The reason for the higher fee is to get it confirmed first to your address before the original or first transaction gets confirmed since the miners prioritizes transactions based on fee rate. It is not different from bumping transactions using RBF this one just sends it back to your own address directly.
Technically you can cancel a bitcoin transaction you can just double spend it to another address using a higher fee
Technically Bitcoin was meant to act as a payment processor and behave somewhat similar to fiat currency. The point was to make a cheaper way to make payments globally. That is why such features were added to it.
As of now with the uncertainty on the transaction fee and how much to spend as the fee is more volatile than the Bitcoin price. I assume such features should be shared with everyone.
Opt "Cancel' transaction in Electrum is somewhat misleading. In fact it creates new (RBF) transaction that returns BTC to the send address of the "canceled" transaction. That is why the fee is increased when comparing it with that one relevant to the "canceled" transaction.
. I am not a technical guy but I am aware of things happening within the Bitcoin ecosystem. I have also seen the cancellation fee being lesser that the transaction fee. The problem here is that I cannot show you but it does happen. 
- and you will be allowed to change the destination. 
