Name That Number

First, we filter out all the names that are not the same length as the number. Then, we iterate over all the digits d in the number. If d does not correspond to a letter in one of the remaining names, we remove that name. Finally, we output all the remaining names.

def trim(num,validNames):
    mapping = {'2':'ABC','3':'DEF','4':'GHI','5':'JKL','6':'MNO','7':'PRS','8':'TUV','9':'WXY'}
    dbg(len(validNames))
    numlen = len(num)
    lengthFittedNames = []
    for name in validNames:
        if len(name) == numlen:
            lengthFittedNames.append(name)
            dbg(f'{name} has been added')
    dbg(len(lengthFittedNames))

    survivedNames = lengthFittedNames
    finalNames = []
    for name in survivedNames:
        for i in range(numlen):
            if not name[i] in mapping[num[i]]:
                break
        else:
            finalNames.append(name)
    return finalNames

with open('dict.txt','r') as d:
    validNames = d.read().split('\n')
with open('namenum.in','r') as fIn:
    res = trim(fIn.read().rstrip(),validNames)
with open('namenum.out','w') as fOut:
    if len(res) == 0:
        fOut.write("NONE")
    else:
        fOut.write("\n".join(res))
    fOut.write("\n")