El Grifo
The heart of the matter here is not about the moral obligation of a company, but about oblligations and entitlements of contract.
In my opinion, as a layman with 30 years of commercial experience involving contracts, it is unreasonable for a company to set a time limit for changes and then fail to give a customer reasonable access to contact the company to make a change within the time limit.
Implied terms and conditions springs to mind, in the sense that if a company says you can change within 7 days, then it implies that you should have the mechanism to change within 7 days and this can be as binding as a written clause.
If this really niggles you, you may wish to consider issuing small claims proceedings against Globespan in the Sheriff's Court, assuming that the contract jurisdiction is Scotland.
You would be claiming for damages and costs arising from the company's alleged breach of contract by failing to provide you with a mechanism to make a change within the 7 day period, so the cost of the unusable flights, the differential cost of replacement flights, telephone calls and correspondence.
Small claims in the sheriff court
Of course there is no guarantee which way the court will find and you might be wise to invest in a telephone call with a suitably qualified lawyer before committing to the cost of the court process, which would include travelling to Scotland for a hearing, but if you are niggled enough, you may find this worthwhile.