C++ Overloading Template Class Function

I am running into this error and not sure how to solve this. What I try to do is to overload the template class function. I think the compiler need some help to determine the type but I'm not sure how.

please any help is appreciated.

thanks

Error in VS 2015; line 41, 47, 53

Error C2664 'void BigALittleA::process(const BigA &,LittleA &)': cannot convert argument 1 from 'const BigB' to 'const BigA &' test c:\test\test\test.h 41 Error C2664 'void BigALittleB::process(const BigA &,LittleB &)': cannot convert argument 1 from 'const BigB' to 'const BigA &' test c:\test\test\test.h 47
Error C2664 'void BigBLittleB::process(const BigB &,LittleB &)': cannot convert argument 1 from 'const BigA' to 'const BigB &' test c:\test\test\test.h 53

Test.h

#ifndef _TEST_H_
#define _TEST_H_

class BigA {};
class BigB {};
class LittleA {};
class LittleB {};

template <typename T1, typename T2>
class Base {
public:
    void process(const T1& t1, T2& t2) {};
};

class BigALittleA : public Base <BigA, LittleA> {
public:
    void process(const BigA& t1, LittleA& t2) {};
};

class BigALittleB : public Base <BigA, LittleB> {
public:
    void process(const BigA& t1, LittleB& t2) {};
};

class BigBLittleB : public Base <BigB, LittleB> {
public:
    void process(const BigB& t1, LittleB& t2) {};
};

class TestMyStuff {
public:

    template <typename T>
    void testMyStuff(const T& t, int whichClass)
    {
        switch (whichClass)
        {
            case 1: // BigALittleA
            {
                LittleA a;
                Aa.process(t, a);   // line 41
                break;
            }
            case 2: // BigALittleB
            {
                LittleB b;
                Ab.process(t, b); // line 47
                break;
            }
            case 3: // BigALittleB
            {
                LittleB b;
                Bb.process(t, b); // line 53
                break;
            }
        }
    }
private:
    BigALittleA Aa;
    BigALittleB Ab;
    BigBLittleB Bb;
};

#endif

Test.cpp

#include "Test.h"

int main(int argc, char** argv) {

    TestMyStuff tms;

    BigA A;
    tms.testMyStuff(A, 1);

    tms.testMyStuff(A, 2);

    BigB B;
    tms.testMyStuff(B, 3);

    return 0;
}