Clutch replaced at a main dealer now the transmission is failing.. related? on 2003 Kia Sedona

Less than one year ago (6000 miles) I had my clutch replaced at a main Kia dealership £800+ It made a funny noise from that point onwards not scary but just different I thought this was just the new clutch. However the noise got louder until I decided to take back to the garage to check. They said it's the transmission and it is failing and to open it up and repair could be £1500. The Kia has only done 74000 miles and has had main dealership services. I feel that the clutch and transmission failing are related ? How could I find out

1 answer 1 comment
should be under warranty,return for insp
The dealer said it's not related to the clutch replacement which is the question.
Can replacing a clutch on a sedona cause damage to the transmission if so how.