If the copy has a thin line edge to edge you need to check what is called the fuser roller. Just before the paper exits the machine it goes through two rollers. Look at these rollers, they look like long cylinders, and see if there is either a scratch or a bubble on the roller. If so, you need to call for service, and have the roller replaced. If not, then more than likely you need a new drum.
Some machines have the drum in an easy to replace cartridge.
If yours is like that, then replace the cartridge. If not, then you must call for service, and have the drum replaced. If you have a moving spot on your copies, the above recommendations apply. If the spot is always in the same place, then there is something on the glass. I can't tell you how many times I've had clients swear the glass was clean, only to locate the spot once I got to the machine.