SUNRISE COLLECTIONS - AT & T Equipment

I was recently alerted to my credit report that collection was created.  The collection originated from AT & T Uverse....  The collection occurred because of equipment that was not returned.  I was unaware that the equipment was not returned and as soon as I became aware I returned the equipment.  I have the receipt that it was returned.  I need to have the collection removed immediately.  What needs to be done in order to make that happen.