Data truncated for column?

Your problem is that at the moment your incoming_Cid column defined as CHAR(1) when it should be CHAR(34).

To fix this just issue this command to change your columns' length from 1 to 34

ALTER TABLE calls CHANGE incoming_Cid incoming_Cid CHAR(34);

Here is SQLFiddle demo

I had the same problem because of an table column which was defined as ENUM('x','y','z') and later on I was trying to save the value 'a' into this column, thus I got the mentioned error.

Solved by altering the table column definition and added value 'a' into the enum set.

By issuing this statement:

ALTER TABLES call MODIFY incoming_Cid CHAR;

... you omitted the length parameter. Your query was therefore equivalent to:

ALTER TABLE calls MODIFY incoming_Cid CHAR(1);

You must specify the field size for sizes larger than 1:

ALTER TABLE calls MODIFY incoming_Cid CHAR(34);