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I think I remember your post on the Payg usage inactivity issue.
It sounds to me that the new SIM card had the Big Value Bundle pre installed on it. But when the agent reversed what happened they should have opted you out. I'm wondering if their system has somehow then reversed that or the agent hadn't properly completed the request.
I understand they ensured you were now on the Payg tariff of choice. The freebie Payg tariff maybe.
Anytime an agent has to log into an account I'm sure it must be logged, so therefore checked to support your timeframe. As I do not have access to Vodafones systems I cannot 100% confirm this.
Phone calls , not all of them however, are recorded and retained for 60 days so you could ask for that to be checked and listened back to.
Vodafone have a Code of Practice which allows a person to take matters further. Vodafone Code of Practice.
That said we do have official Vodafone Tech Teams here who read all posts and help where they can. Perhaps let them catch up with your thread and engage with you.
I hope you reach a satisfactory resolution to this.
I'm sorry to hear what has happened, and I do hope that you can get it resolved, as outlined by BandOfBrothers.
On a matter simply related to using the SOS facility on your mother's phone, can I offer something I realised while helping my elderly mother-in-law who was in a similar situation.
The SOS button on the phone is very useful for raising help very quickly, but, if it is set to call a family member or friend, it is dependent upon having credit and a signal from the network you have chosen, in this case Vodafone.
On the other hand, if the SOS button is set to dial 999, it will do so even if there is no credit, or if it is only another network which is available. Under Ofcom rules, all networks have to make their service available to any caller who dials 999.
I was recently able to check a friend's phone, who had let her number expire through lack of use - it was still offering the emergency call service, although the SIM was dead for all other purposes. Though I would stress that it was a relatively modern phone - it's possible that older phones, manufactured before Ofcom introduced its ruling, might not have this facility.