TMOG4AR Gateway

This morning my internet went out completely for about an hour and then gave me absurdly low download speeds (1 - 2 mbps) for another hour. So, I called T-Mobile technical support to try to swap what I have for one of the 2 new gateways. I explained that I need one of them so I will be able to connect an external antenna if the internal ones don't give me a stronger, more reliable signal. I spent over an hour on the phone with them first speaking to one of their reps and then speaking to a supervisor. They told me that the best they could do was to swap the Arcadyan KVD21 I currently have with another of the same as a warranty exchange. I explained that the gateway I am using isn't broken or defective but that it doesn't have the ability to bring in a strong enough signal that one of the new ones will. They checked with the local stores to see if they have one available for me to swap (at a $35 fee, by the way), which they didn't. They said they have no way to request a specific gateway, that they are chosen at random. However, they also told me that there is a high demand for these new devices. I asked how that could be if specific models couldn't be requested. His answer was "that's a good question". So, here I am left frustrated with no apparent solution. I do not want to go back to Xfinity but if this becomes a consistent problem I don't know what other choices I have. Thanks for all who spent the time to read this very long story.