I had this problem a while ago after I got throttled and restarted a new month. VM did a data reset and it was fine after.
Also,I noticed that prior to the Network Vision update in our area, the phone went very often into 1x. (Network Vision is the new Sprint's tower equipment that transmit enhanced 3G and LTE)
Contact their social media people: email@example.com
, it is easier than talking to someone outside the US for an hour.