I need to display a simple map in html with only at&t coverage and allow users the ability to input their own address to check their own area.
Also, I need to make sure not to mention “at&t” anywhere on the website, as this would circumvent our reseller agreement.
Can you please be kind to tell mw what code I can put in an iframe to to this.
You need to learn program with e.g. Leaflet or OpenLayers.
Furthermore you need to include a geocoder for address lookup. Nominatim is such a geocoder, depending on the usage of your application you might have to deploy your own server.
Of course you want a map to be displayed as well, therefore you need a tile server. Again depending on the usage of your website, you might have to deploy your own server, or use e.g. Mapbox which has payed options depending on your needs.
Maybe you should immediately take a look at Mapbox (or similar companies) and see whether they provide a service that fit your needs.