If your end users are facing issues with storage size, you have three options to get them more storage.
1) Purchase a storage license for your account - https://support.google.com/a/answer/1047457
This option is to purchase a storage license account directly for your account. This is not transferable and if you were to delete your account it would be deleted. Included in the link are the instructions on how to add the license and the various price/sizes options. This is something you would handle without Dito.
2) Purchase a storage license for your domain - https://support.google.com/a/answer/1726914
This option is to purchase a storage license for your domain that is then assigned to you. This is transferable so should you no longer need the license you can transfer it to someone else. These are renewed monthly. The link above can walk you through how to assign and if you need to purchase a license we can coordinate that.
3) Upgrade to Google Business/Enterprise - https://support.google.com/a/answer/177064?hl=en
This option would be to upgrade the license types for your domain. All business/enterprise level customers have unlimited storage. This would be something Dito would handle.