Why isn't my sim card being recognized and why do I get i.e displaying 'insert sim' when sim is installed?

[AC Question]

sim card not recognised i.e displays 'insert sim' when sim is installed

Samsung s111 mini GT-18190N
The phone was unlocked before being passed 'UP' to me, unfortunately the unlock was not a full success. The phone was with Vodafone and my network is also with Vodafone but through Sainsbury. Took the phone to their counter, tried another sim but no good. They could not give any more help.
Have tried 'Factory Reset' as Vodafone site but still does not recognise sim.

Any thoughts

Thanks Ray