got card but can't use it

Hi

I  purchased one of those mobile hotspot devices off ebay and decided to try the £9 SMARTY data only card. 

I received my SIM the other day but the seller sent me wrong device (has no SIM slot) I have to return it after bank holiday ..so my issue is I couldn't start my month trial on 1st May as planned to try SMARTY for the month. 

Also I don't think I could download an app the 'data hotspot only' devices to activate the SIM as I don't want to put it in my mobile ...my plan was for it to be spare data only for when I'm downloading games. 

so will I now not get a full month as I don't have the device to put the SIM in as soon as it arrived?  or does the month count from the date I activate it?  

Also how often do I  have to buy a data pack to keep the SIM active?  ..could data be carried over if I didn't use it all in one month? 

Thanks