This is funny. You have been trading for a week and are already blaming your losses on boogiemen.
You should review the OCC paperwork you signed.
http://www.cboe.com/education/getting-started/quick-facts/expiration-exercise-assignment
The CBOE has a quick sheet for you. The relevant section is as follows:
These are the rules of the game. In other words they will force you to meet margin or close it due to this rule. Moneyness matters here. Since we are talking about expiration, the type of expiration you are referring to only deals with ITM options. You are responsible for closing your contracts before expiration. The only people who carry them to expiration ITM are people who have an intention to exercise (for long options).
Why would you carry an ITM option to expiration only to not exercise it? Exercise allows you to achieve your maximum profit assuming the equity goes to the moon (call) or falls through the floor (put).
Or on the contrary (related to getting margin called), imagine you allow someone to carry an ITM short option to expiration and then they call your options desk and say "I dont have enough money to cover this trade, help me". The OCC is looking out for themselves here - as they should.
I would recommend you stop trading options for now and pick up a few books on the subject. Options are very complicated instruments and you need to understand all the rules of the game before playing.