I am facing a similar problem with Rain. I was getting less than 1MB/s download speed and up to 4MB/s upload using internal antenna on Huawei B525. I read somewhere that an LTE antenna would help me and I purchased an XPOL-6 High gain antenna. Put it up and only managed to get 1MB/s gain with...
I guess I'm late to the party but anyway some people are actually asking the same question in 2020 lol! There is an app on Playstore called Opensignal, it gives you all the information about your carrier.