You can see the remaining credit of your roaming package at any time in your customer account. 

You can find a step by step guide here:

  1. Log in to your customer account.
  2. On your Dashboard navigate to the SIM card where you want to see the remaining roaming balance.
  3. Select the according SIM card with one click
  4. Select "Roaming" in the upper right corner 
  5. Now you see your remaining roaming credit in the right circle