SQLSERVER 2014:- Invalid length parameter passed to the LEFT or SUBSTRING function : I am getting the following error while trying to execute the below query in sql server 2014 . I have data customers chat data and I want to replace the customers with "Customer" and Agent name with "Agent"

Error :- Invalid length parameter passed to the LEFT or SUBSTRING function.

Data format : - 

11:35:41 Daniella Sichtman : I don't mind. It's ok 
11:35:55 Daniella Sichtman : Did you understand my problem? 
11:36:09 Madan : Yes, I got your issue. 
11:36:20 Madan : Please stay connected while I check what best I can do for you. 
11:37:01 Daniella Sichtman : OK. If I may suggest. Mail the hotel that we need 2 nights. I have their contact information if you need that. 
11:37:21 Daniella Sichtman : The room are availible they told us 
11:37:41 Daniella Sichtman : Just need an ok 
11:37:43 Madan : Have you visited the hotel reception to extend your stay ? 
11:38:01 Daniella Sichtman : Yes. They told us you need to give the ok 
11:39:14 Madan : Nico, I would like to Inform you that we have already authorized to the hotel to extend the stay for our guests. 
11:39:46 Daniella Sichtman : They don't know about that or did you told them this morning? 


Note:- I have seen many post but did't get the desire output. I would request to all of you , could you help me.

Regards
Anand



XX:XX:XX Agent : I do understand what you are saying but I am afraid, but any instrument larger than XXcm x XXXcm x XXcm like a double bass or harp can’t be taken on board the aircraft as cabin baggage. 
XX:XX:XX Customer : Hello, it's a GUITAR. it is just X cm bigger, the case is Xcm thicker. 
XX:XX:XX Customer : it's a soft case that can be pushed to fit your dimensions 
XX:XX:XX Agent : I do understand what you are saying but even it is X cm then also they will ask you to put it on hold and we do understanbd that you are worried if it gets damaged but there won't be any case and you can get the fragile tag from the Airport so that it will be taken care.<br /> 
XX:XX:XX Customer : What if I take it on board (priority boarding) and it fits within their dimensions exactly and can go in an overhead locker?