Car won't start after having oil change. Started easily before.

What is your question?

In freezing weather car starts and runs very well. However, after bringing in for oil change (and a check for an oil leak), now it doesn't start easily. It keeps trying to turn over and when I hear it almost 'catch', I pump the gas pedal, revving it and it starts. I don't understand the correlation between getting an oil change and my car developing starting problems. It is not the battery. I think it is a fuel delivery issue. Kindly provide some guidance. Thank you.