Medi gap G insurance

I had asked about changing medigap Supplement G to a less expensive company. WE now have Aetna and it is nearly $1000 a month. I thought perhaps we could get a different company that was less expensive. I do not want an Advantage Plan as I don’t trust they will be there when we need it. I did check a lot and if the only reason you are wanting to change companies is price you cannot.
So if I’m wrong and you can help me find less expensive MediGap Plan G insurance I sure would appreciate it. Thanks so much replying and for asking for more info.