Dropdown value not updated for call type field

Steps:

Login with portal
1. Go to Tarrif > Call type
2. Now create one call types record
3. Now go to Tarrif > Origination rates
4. Now use above created call type in any rate group
5. After use again set call type field - Select and save the record
6. Now again open origination rate and check

Expected result : Call type field should be updated successfully.

Actual result : Call type field is not updated for 'Select' value and above used call type value already display.