If it was indeed some sort of "fee" that you got hit with, I doubt they will be BTC transactions fees. These are measured in satoshis/Byte and generally aren't very large. If you look at: https://bitcoinfees.21.co/ you can get an idea of the BTC transaction fees people are using...
As at 1000 UTC 2017-02-17:
Quote
The fastest and cheapest transaction fee is currently 0.0000014 BTC/byte, shown in green at the top.
For the median transaction size of 226 bytes, this results in a fee of 0.0003164 BTC.
For the median transaction size of 226 bytes, this results in a fee of 0.0003164 BTC.
0.00031640 BTC is ~$0.33c at current prices.
NOTE: Transaction fees are purely voluntary, you can technically choose whatever you like as a fee, even zero... just don't expect miners to include your transaction if you use a low or no fee.
EDIT:
OK, so I just checked out the BUY/SELL option in Mycelium...
Simplex wants USD$1200 to buy 1 BTC... the current going rate is around $1050... that is just a RIDICULOUS markup!!?! Indeed, putting in $50 it tells me I'll get 0.03465495 BTC... which is roughly USD$36. So, it seems you just got ripped off by Simplex. Such a shame they are being promoted by Mycelium.
Caveat Emptor
