In my case, I was having a similar problem:
/usr/bin/ld: Bank.cpp:(.text+0x19c): undefined reference to 'Account::SetBank(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >)' collect2: error: ld returned 1 exit status
After some researches, I realized that the problem was being generated by the way that Visual Studio Code was compiling the Bank.cpp file. So, to solve that, I just prompted the follow command in order to compile the c++ file sucessful:
g++ Bank.cpp Account.cpp -o Bank
With the command above, It was able to linkage correctly the Header, Implementations and Main c++ files.
OBS: My g++ version: 9.3.0 on Ubuntu 20.04