Utilize the Cloud Natural Language API to extract custom entities for classification, considering its ease of integration and predefined models.

Develop a custom model from scratch to identify product keywords from the transcribed calls and then apply a classification algorithm, offering maximum customization but requiring significant development effort.

Employ AutoML Natural Language to extract custom entities for classification, leveraging its ability to automatically identify and extract custom entities with minimal preprocessing.

Use the AI Platform Training built-in algorithms to create a custom model, which may require additional feature engineering but offers flexibility in model selection.

Combine the use of AutoML Natural Language for entity extraction with a custom classification algorithm for finer control over the classification process, balancing between development time and customization.