Calling ISP is not only to help to get faster internet.
Try to keep in mind the following instructions
1.Get a download accelerator
2.Turn off all unused apps while downloading
3.Don't upload information while you're downloading
4.You must always keep your computer clean of any viruses
5.clear your temporary download history files.
6.Use latest version of any browser
7.Do regular speed test.
When i had the same problem,i followed the same ways and my internet speed increased than before by testing internet speed using ScanmySpeed.com.
I am sure,it's very useful to get faster internet.