here's how FDA defines the procedures for handling complaints; you can certainly consider the reference as base and customize it as per your requirements; and the following reference may cover the associated regulatory processes which may not be relevant for your scenario.
scroll through the page and you will find an sample procedure in the later part of the page.
and as far as complaint definition is concerned...FDAs definition goes like this..
"A "complaint" is any indication of the failure of a device to meet customer or user expectations for quality or to meet performance specifications. Thus, any written, oral, or returned goods expression of dissatisfaction relative to the identity, quality, durability, reliability, safety, effectiveness, or performance of any device manufactured by this manufacturer would be considered a complaint. "
as far as the evaluation/classification is concerned...as per the above referred document..."Service or repair data shall be reviewed [820.200(b)&(e)] to identify systematic problems and problems that may qualify as complaints. When these problems are identified they should be processed as complaints according to the requirements in 820.198. "
each service call could be evaluated if it match any of the criteria mentioned for it to be considered as complaint. [refer above webpage..]
1. PRODUCT PERFORMANCE: the product in some way does not perform to user's expectation or to any level of performance conveyed to the customer by printed labeling or verbally by company employees.
2. PRODUCT SAFETY: all safety complaints are covered by this procedure.
3. PRODUCT RELIABILITY: failure rate or need for service adjustments greater than user expectation, i.e. beyond the tolerable level of expected wear or malfunction.
4. PRODUCT APPEARANCE: visual defects inconsistent with the user's expectations for a medical device.
5. GENERAL COMPLAINTS: order or shipping error, delayed or unacceptable response to problems, unfulfilled promises, etc.
6. MDR REPORTABLE COMPLAINTS: all complaints involving device-related deaths, serious injuries and malfunctions. (See Policy/Procedure No. XXX for handling of MDR reports.)
hope that helps.