You could use a "simple case" expression (in contrast with the searched case expression you wrote).

SELECT CASE RTRIM(Customer.Source)

WHEN 'CREDITNEW' THEN 'CREDIT'

WHEN 'CREDITOLD' THEN 'CREDIT'

WHEN 'TOC' THEN 'CREDIT'

WHEN 'DEBIT' THEN 'UC DEBIT'

WHEN 'DEBITOLD' THEN 'DEBIT' -- Defined orginally with space

WHEN 'DEBITNEW' THEN 'DEBIT' -- Crystal uses the space version for logo

WHEN 'TLC' THEN 'DEBIT'

ELSE 'UNDEFINED' -- Default logo

END AS CompanyName, CompanyId, TermsofUse

FROM Customer