Hello,
First of all remember that big devices such as phablets, tablets, laptops, desktops etc. Have more wifi reception power than phones. It is very much possible that if your ate using your iphone and macbook together at one time... On one wifi then the macbook wil be quite faster than the on your iphone.
Secondly, if you are not using it at the same time check weather your phone has some wifi updates on the go. But if it is the first case then, it is normal.
Hope your question was answered.