Offer a Pensioner-Friendly VOIP Service

Is it technically possible to offer a VOIP service where call failure reasons are spoken (and explained) rather than coming back as digits on the handset display in the style of HTTP status codes? At the cost of not being fully standards-compliant.

My parents are in their late 80's, and will soon move to sheltered housing with FTTC on offer. They will want broadband so I'll recommend they stay with AAISP. It would be nice to use AAISP as single supplier for both the phone line and the FTTC service, so that my aged parents never have to queue up to speak to a BT call centre script bunny when something breaks (or the installation engineer doesn't turn up).

If they went for AAISP VOIP (maybe with a Gigaset VOIP DECT handset) I think they would get confused by the error codes on the handset. I find these confusing myself, trying to remember which codes mean invalid number, subscriber engaged, call price exceeded, etc. So it would be nice to offer a VOIP service where the caller experience was more like what users are accustomed to with BT lines (just without the high call prices).

Thanks

- Martin