“Called on the mat” – being reprimanded by someone in authority. informal. This idiom is a military reference: the orderly room mat was where a soldier accused of some misdemeanour would stand before the commanding officer.

Mark 2 (NRSV)
9 Which is easier, to say to the paralytic, ‘Your sins are forgiven,’ or to say, ‘Stand up and take your mat and walk’? 10 But so that you may know that the Son of Man has authority on earth to forgive sins”—he said to the paralytic— 11 “I say to you, stand up, take your mat and go to your home.” 12 And he stood up, and immediately took the mat and went out before all of them; so that they were all amazed and glorified God, saying, “We have never seen anything like this!”

Mark 2 (The Message)
8-12 Jesus knew right away what they were thinking, and said, “Why are you so skeptical? Which is simpler: to say to the paraplegic, ‘I forgive your sins,’ or say, ‘Get up, take your stretcher, and start walking’? Well, just so it’s clear that I’m the Son of Man and authorized to do either, or both . . .” (he looked now at the paraplegic), “Get up. Pick up your stretcher and go home.” And the man did it—got up, grabbed his stretcher, and walked out, with everyone there watching him. They rubbed their eyes, stunned—and then praised God, saying, “We’ve never seen anything like this!”