I applied a Deterministic case insensitive encryption on contact.name field, And whenever I use it in a WHERE clause of SOQL query, it throws me an Field 'Name' can not be filtered in a query call. I though if you apply Deterministic Encryption to a field you can use it in SOQL Where clause? Need help for this one.
This is expected behavior. When you encrypt contact name we're actually encrypting first name and last name separately. See the linked help article which explains the considerations for deterministic encryption, as it has a section dedicated to this and provides a workaround.