Yes, it is typically possible to change the storage size after reserving a container with 1-800-PACK-RAT. Customers often find themselves needing a different size as their needs evolve, and the company strives to accommodate those changes. However, this process may vary based on factors such as availability and specific regional policies. It is advisable to check the current web page for detailed information or updates regarding any restrictions or procedures involved in modifying your reservation. Ultimately, ensuring that your storage requirements are met is important, and 1-800-PACK-RAT aims to provide flexible options for its customers.