Whenever you like you can upgrade the service from the Additional services area of the website domains.aruba.it. This procedure allows you to increase the whole space available of the 5 databases: every 1GB package costs 7 euro (+VAT). 
The update has the same duration as the original database. Therefore if the MySql is close to its expiration date first you will need to carry out the renewal order and then make an upgrade of the space.