No feedback, no action, no resolve

I renewed my contract on 16 April 2019, however the phone associated with the new contract is not suitable for my need (64GB which is way too small) and I've requested that the device be collected & my contract cancelled on several occasions. I've logged calls almost daily. I've emailed Customer Service on several occasions. In the last month I've received plenty of promises of call backs, I even got a reference number ( ********** ) with a promise of a courier arrangement 10 days ago, but still nothing. It has been the most frustrating process with absolutely no resolve. I hate having to review a company online - but I'm at my wits end and don't know what else to do!