Hello @nmnmnm,
A phone number cannot be active on two SIM at the same time as for the person that said they got a call from your number it could mean that scammers spoof your number to make it show that call is coming from your number on the other person's phone, this has been an ongoing thing for years and the carriers haven't quite got a grip on combating this as yet they are working on implementing a technology called STIR/SHAKEN you can get more info here.
Fido has implemented something called Spam Call Detect you can get more info here, While this will help incoming calls to Fido customers it will not help the other party if they have a different carrier that hasn't implemented any spam detection technology.
As for the long-distance calls could it be you got a call from a number that you redial without knowing it's not a Canadian number? I would suggest you reach out to customer service in regards to this and they can go over your invoice and will be better able to assist you.
