iPad Mini will not connect to 4g Vodafone (UK)

Hi There,

I have a first generation iPad Mini with a Vodafone data contract.

The iPad will connect fine with 3G but will not connect to any form of 4G (i.e. "4G" or "LTE").

I have:

- checked my iPad (having restored it completely)

- enabled LTE on the settings

- checked my contract (definitely a 4G contract)

- checked the coverage area (covered fully - inside and outside)

and all have not helped in making any 4G connection.

Vodafone's response (when I asked them) was to take it to Apple but I'm wondering if anyone knows what has gone wrong?

Many thanks.