Well, first of all your reaction is not balanced
https://www.thoughtco.com/definition-of-double-replacement-reaction-605046
C+4 4H- ????
whoa!, No such ions
This is not an ionic bond. C and H share electrons to make the hydrocarbon CH4 methane
CH4 + Cl2 → CH4Cl + HCl
Is this a double replacement reaction? I believe it is but am not entirely sure.
2 answers
To extend the answer from Damon, you probably meant CH3Cl + HCl. This is not a double replacement reaction. It is a redox reaction. In some organic circles this is called a substitution reaction; i.e., you're substituting a Cl atom for a H atom.