Refused Service for battery replacement

Just visited the Apple Store in Solihull UK expecting to pick up my daughter's iPhone 6 after a battery replacement. However, to my surprise, I was advised that service had been refused because the battery had been 'modified' and that to replace the battery would be a health and safety issue.

The phone was bought from new on contract and has never previously been opened or serviced. The technician stated that the battery had a single central adhesive tab and that Apple only manufactured the iPhone 6 with two adhesive tabs. The battery had therefore been modified.

Before I go back to my phone contract company to complain about being supplied a refurbished phone which Apple were going to refuse to service, can anyone advise. if iPhones were only manufactured with two adhesive battery tabs.